<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019edbbc-1446-74aa-aec8-1db16265d976,g:7b0424eb-5e17-4f25-90df-636a682bcc69-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.bxp.com/role/Cover" xlink:type="simple" xlink:href="bxp-20260630.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1e05-78ed-9959-c4d8302d3c67" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntitiesTable_019edbbc-1e05-78ed-9959-c4d8302d3c67" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-70d2-a639-4f81ac22133d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-78ed-9959-c4d8302d3c67" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-70d2-a639-4f81ac22133d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-70d2-a639-4f81ac22133d_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-70d2-a639-4f81ac22133d" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-70d2-a639-4f81ac22133d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-772d-be00-f9ea3503951a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-70d2-a639-4f81ac22133d" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-772d-be00-f9ea3503951a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedParntershipMember_019edbbc-1e05-7978-9b51-859ba6fac561" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedParntershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-772d-be00-f9ea3503951a" xlink:to="loc_bxp_BostonPropertiesLimitedParntershipMember_019edbbc-1e05-7978-9b51-859ba6fac561" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7a79-97a8-e6f0d4716ead" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-772d-be00-f9ea3503951a" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7a79-97a8-e6f0d4716ead" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019edbbc-1e05-794c-9870-b7a4b72b67d8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentType_019edbbc-1e05-794c-9870-b7a4b72b67d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019edbbc-1e05-7da2-a47e-8539319b19c0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentQuarterlyReport_019edbbc-1e05-7da2-a47e-8539319b19c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentAnnualReport_019edbbc-1e05-7151-be10-a856433bc621" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentAnnualReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentAnnualReport_019edbbc-1e05-7151-be10-a856433bc621" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019edbbc-1e05-7fde-b31b-beb016ad9f6d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentPeriodEndDate_019edbbc-1e05-7fde-b31b-beb016ad9f6d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019edbbc-1e05-75b0-8581-ed43d42ab608" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentTransitionReport_019edbbc-1e05-75b0-8581-ed43d42ab608" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019edbbc-1e05-7e1a-8e8d-67128cd11d13" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityFileNumber_019edbbc-1e05-7e1a-8e8d-67128cd11d13" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019edbbc-1e05-7a78-9e8a-661afb6358c5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityRegistrantName_019edbbc-1e05-7a78-9e8a-661afb6358c5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019edbbc-1e05-7a6e-b732-1ad76a80ecdb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityCentralIndexKey_019edbbc-1e05-7a6e-b732-1ad76a80ecdb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019edbbc-1e05-7cb3-b838-0f4fbf7590ed" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_CurrentFiscalYearEndDate_019edbbc-1e05-7cb3-b838-0f4fbf7590ed" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019edbbc-1e05-71c8-9a7b-2151c245dcd4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentFiscalYearFocus_019edbbc-1e05-71c8-9a7b-2151c245dcd4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019edbbc-1e05-7fca-9889-a0f5943eab2e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019edbbc-1e05-7fca-9889-a0f5943eab2e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019edbbc-1e05-7460-b9af-6ee0447a092c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_AmendmentFlag_019edbbc-1e05-7460-b9af-6ee0447a092c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019edbbc-1e05-7765-8cb9-667d82763d79" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019edbbc-1e05-7765-8cb9-667d82763d79" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019edbbc-1e05-7c7e-91ad-b85d40bcacbd" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityTaxIdentificationNumber_019edbbc-1e05-7c7e-91ad-b85d40bcacbd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019edbbc-1e05-7839-baef-0c202f57a51e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityAddressAddressLine1_019edbbc-1e05-7839-baef-0c202f57a51e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019edbbc-1e05-754c-9b62-a3e3411245bc" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityAddressCityOrTown_019edbbc-1e05-754c-9b62-a3e3411245bc" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019edbbc-1e05-717b-9e59-dd21ca025c6e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityAddressStateOrProvince_019edbbc-1e05-717b-9e59-dd21ca025c6e" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019edbbc-1e05-7e50-94e8-1af5f45923fd" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityAddressPostalZipCode_019edbbc-1e05-7e50-94e8-1af5f45923fd" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019edbbc-1e05-7d92-9e84-71f0f4c0d9e7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_CityAreaCode_019edbbc-1e05-7d92-9e84-71f0f4c0d9e7" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019edbbc-1e05-739f-abf5-14cfc37b734b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_LocalPhoneNumber_019edbbc-1e05-739f-abf5-14cfc37b734b" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationFormerLegalOrRegisteredName_019edbbc-1e05-75f3-b6aa-de384796d58a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationFormerLegalOrRegisteredName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityInformationFormerLegalOrRegisteredName_019edbbc-1e05-75f3-b6aa-de384796d58a" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019edbbc-1e05-78d5-bb30-0e6a8594b365" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_Security12bTitle_019edbbc-1e05-78d5-bb30-0e6a8594b365" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityListingParValuePerShare_019edbbc-1e05-74ed-acb6-671043f4c0b9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityListingParValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityListingParValuePerShare_019edbbc-1e05-74ed-acb6-671043f4c0b9" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019edbbc-1e05-7a11-a9da-2ec3676af5b5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_TradingSymbol_019edbbc-1e05-7a11-a9da-2ec3676af5b5" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019edbbc-1e05-702e-9d0c-74a845bf8005" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_SecurityExchangeName_019edbbc-1e05-702e-9d0c-74a845bf8005" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12gTitle_019edbbc-1e05-701d-939b-fc77b8d1a07c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12gTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_Security12gTitle_019edbbc-1e05-701d-939b-fc77b8d1a07c" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityWellKnownSeasonedIssuer_019edbbc-1e05-7042-a787-612552d41ca0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityWellKnownSeasonedIssuer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityWellKnownSeasonedIssuer_019edbbc-1e05-7042-a787-612552d41ca0" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityVoluntaryFilers_019edbbc-1e05-7b61-b07b-fa6d6092c888" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityVoluntaryFilers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityVoluntaryFilers_019edbbc-1e05-7b61-b07b-fa6d6092c888" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019edbbc-1e05-7824-9a47-124395307bf8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityCurrentReportingStatus_019edbbc-1e05-7824-9a47-124395307bf8" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019edbbc-1e05-755d-8d75-b468b8ed50f3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityInteractiveDataCurrent_019edbbc-1e05-755d-8d75-b468b8ed50f3" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019edbbc-1e05-7d7f-a3e2-a1027b180cea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityFilerCategory_019edbbc-1e05-7d7f-a3e2-a1027b180cea" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019edbbc-1e05-7ab1-bc05-0cfd3b815e06" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntitySmallBusiness_019edbbc-1e05-7ab1-bc05-0cfd3b815e06" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019edbbc-1e05-75ec-899b-e38bcbec004f" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityEmergingGrowthCompany_019edbbc-1e05-75ec-899b-e38bcbec004f" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_IcfrAuditorAttestationFlag_019edbbc-1e05-7716-837f-f54a7882b91d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_IcfrAuditorAttestationFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_IcfrAuditorAttestationFlag_019edbbc-1e05-7716-837f-f54a7882b91d" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFinStmtErrorCorrectionFlag_019edbbc-1e05-7906-96ae-fa2a1d937c6c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFinStmtErrorCorrectionFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentFinStmtErrorCorrectionFlag_019edbbc-1e05-7906-96ae-fa2a1d937c6c" xlink:type="arc" order="34"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019edbbc-1e05-749a-9ef8-b6d0a0fdbcc8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityShellCompany_019edbbc-1e05-749a-9ef8-b6d0a0fdbcc8" xlink:type="arc" order="35"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityPublicFloat_019edbbc-1e05-7bc4-9fd4-b8014f7bbb8b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityPublicFloat"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityPublicFloat_019edbbc-1e05-7bc4-9fd4-b8014f7bbb8b" xlink:type="arc" order="36"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentsIncorporatedByReferenceTextBlock_019edbbc-1e05-7e0d-93dd-3983ffa9922d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentsIncorporatedByReferenceTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_DocumentsIncorporatedByReferenceTextBlock_019edbbc-1e05-7e0d-93dd-3983ffa9922d" xlink:type="arc" order="37"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019edbbc-1e05-7afa-ad41-036412cc5006" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019edbbc-1e05-7051-bc9c-8e34b9e9c906" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019edbbc-1e05-7afa-ad41-036412cc5006" xlink:type="arc" order="38"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-775d-ab65-f8b020bac50d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-762e-8d9d-eb3b3bb1aa31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-775d-ab65-f8b020bac50d" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-762e-8d9d-eb3b3bb1aa31" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-7695-8945-278b5e19e1b2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-762e-8d9d-eb3b3bb1aa31" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-7695-8945-278b5e19e1b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7695-8945-278b5e19e1b2_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7695-8945-278b5e19e1b2" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7695-8945-278b5e19e1b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7cf6-998c-1a4c54ab741b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7695-8945-278b5e19e1b2" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7cf6-998c-1a4c54ab741b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7160-a01c-04f3e7606bab" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7cf6-998c-1a4c54ab741b" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7160-a01c-04f3e7606bab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019fbd32-17fb-74be-85b7-7d58d114bb59" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-762e-8d9d-eb3b3bb1aa31" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019fbd32-17fb-74be-85b7-7d58d114bb59" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019fbd32-17fb-74be-85b7-7d58d114bb59_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019fbd32-17fb-74be-85b7-7d58d114bb59" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019fbd32-17fb-74be-85b7-7d58d114bb59_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019fbd32-5fe0-79da-b81f-0f388f79ef0c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019fbd32-17fb-74be-85b7-7d58d114bb59" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019fbd32-5fe0-79da-b81f-0f388f79ef0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019fbd32-cbc4-7926-986d-490b67cfc202" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019fbd32-5fe0-79da-b81f-0f388f79ef0c" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019fbd32-cbc4-7926-986d-490b67cfc202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1e05-7687-9f7d-9d54b2037e23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-762e-8d9d-eb3b3bb1aa31" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1e05-7687-9f7d-9d54b2037e23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-7687-9f7d-9d54b2037e23_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1e05-7687-9f7d-9d54b2037e23" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-7687-9f7d-9d54b2037e23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-743d-a092-bb971cbe1a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1e05-7687-9f7d-9d54b2037e23" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-743d-a092-bb971cbe1a72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019edbbc-1e05-71f4-9d15-a8baf4fa06b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-743d-a092-bb971cbe1a72" xlink:to="loc_us-gaap_NonrelatedPartyMember_019edbbc-1e05-71f4-9d15-a8baf4fa06b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019edbbc-1e05-7ced-85d0-8db3265a0778" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019edbbc-1e05-743d-a092-bb971cbe1a72" xlink:to="loc_us-gaap_RelatedPartyMember_019edbbc-1e05-7ced-85d0-8db3265a0778" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-775d-ab65-f8b020bac50d" xlink:to="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019edbbc-1e05-7bd5-ae78-d128bb2545f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019edbbc-1e05-7bd5-ae78-d128bb2545f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization_019edbbc-1e05-7fdc-b8ff-c94ac335eda4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization_019edbbc-1e05-7fdc-b8ff-c94ac335eda4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1e05-73c8-9180-8337117e178f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1e05-73c8-9180-8337117e178f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1e05-7044-9296-52f3503c21ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1e05-7044-9296-52f3503c21ef" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1e05-7f82-a556-1c0b11f15097" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1e05-7f82-a556-1c0b11f15097" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-77f8-a7af-81cfa3f6f790" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-77f8-a7af-81cfa3f6f790" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7f9a-bb46-db2047f21e3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7f9a-bb46-db2047f21e3d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketableSecurities_019edbbc-1e05-7e6f-a49a-de0d02a47cc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_MarketableSecurities_019edbbc-1e05-7e6f-a49a-de0d02a47cc3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_019edbbc-1e05-7e15-8107-c20319b24bd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_AccountsReceivableNet_019edbbc-1e05-7e15-8107-c20319b24bd2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_019edbbc-1e05-769d-8e1a-b6dd49625e6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_NotesReceivableNet_019edbbc-1e05-769d-8e1a-b6dd49625e6b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent_019edbbc-1e05-7ad7-9345-5b8ff96e7c46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent_019edbbc-1e05-7ad7-9345-5b8ff96e7c46" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentReceivablesNet_019edbbc-1e05-753b-ab42-28a43d11ffa2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredRentReceivablesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_DeferredRentReceivablesNet_019edbbc-1e05-753b-ab42-28a43d11ffa2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCosts_019edbbc-1e05-772f-be9b-6617136b4b7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_DeferredCosts_019edbbc-1e05-772f-be9b-6617136b4b7b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-70b1-a6c1-b93f3b0a1ce2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-70b1-a6c1-b93f3b0a1ce2" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1e05-71d6-9417-efe308a17851" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1e05-71d6-9417-efe308a17851" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_019edbbc-1e05-7f3c-82a4-578ad24b8b5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_019edbbc-1e05-7f3c-82a4-578ad24b8b5f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019edbbc-1e05-72e5-b78d-a8c186ae994f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1e05-7759-9425-bd675754d347" xlink:to="loc_us-gaap_Assets_019edbbc-1e05-72e5-b78d-a8c186ae994f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-775d-ab65-f8b020bac50d" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_019edbbc-1e05-7e09-8e20-ff22db0333e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_SecuredDebt_019edbbc-1e05-7e09-8e20-ff22db0333e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019edbbc-1e05-7386-9221-ff46627f640a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_SeniorNotes_019edbbc-1e05-7386-9221-ff46627f640a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebt_019edbbc-1e05-7dc4-b04e-2120564b6a9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_ConvertibleDebt_019edbbc-1e05-7dc4-b04e-2120564b6a9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019edbbc-1e05-7b32-b9ed-321df7e30d10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_LineOfCredit_019edbbc-1e05-7b32-b9ed-321df7e30d10" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherBorrowings_019edbbc-1e05-743d-95da-fbb23996d79b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_OtherBorrowings_019edbbc-1e05-743d-95da-fbb23996d79b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaper_019edbbc-1e05-7116-be6a-a852c01f3c13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_CommercialPaper_019edbbc-1e05-7116-be6a-a852c01f3c13" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_019edbbc-1e05-7432-bfa1-c61cbf86d2c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_FinanceLeaseLiability_019edbbc-1e05-7432-bfa1-c61cbf86d2c4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019edbbc-1e05-747b-9227-e4ceeb9b0832" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_OperatingLeaseLiability_019edbbc-1e05-747b-9227-e4ceeb9b0832" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1e05-7850-aa08-cca18889247e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1e05-7850-aa08-cca18889247e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019edbbc-1e05-7f59-8522-88ee7d772a24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019edbbc-1e05-7f59-8522-88ee7d772a24" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019edbbc-1e05-77e9-b8a6-0de550b88c48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_InterestPayableCurrentAndNoncurrent_019edbbc-1e05-77e9-b8a6-0de550b88c48" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019edbbc-1e05-7f30-ac17-7604ca0ba074" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_OtherLiabilities_019edbbc-1e05-7f30-ac17-7604ca0ba074" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_019fb4d8-df40-7417-99b4-888594ee5992" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_019fb4d8-df40-7417-99b4-888594ee5992" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019edbbc-1e05-73a4-a8a0-279563542166" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAbstract_019edbbc-1e05-7548-90dd-3958f064ad03" xlink:to="loc_us-gaap_Liabilities_019edbbc-1e05-73a4-a8a0-279563542166" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019edbbc-1e05-73ab-985f-7d1a9f114bb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019edbbc-1e05-73ab-985f-7d1a9f114bb0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_019edbbc-1e05-7971-9573-7a46b6d21755" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_019edbbc-1e05-7971-9573-7a46b6d21755" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessStockSharesOutstanding_019edbbc-1e05-73a5-be83-22d175895c66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_ExcessStockSharesOutstanding_019edbbc-1e05-73a5-be83-22d175895c66" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessStockSharesIssued_019edbbc-1e05-7103-82ac-8362cec11732" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_ExcessStockSharesIssued_019edbbc-1e05-7103-82ac-8362cec11732" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019edbbc-1e05-78fa-bff7-836aaba51b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019edbbc-1e05-78fa-bff7-836aaba51b3a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019edbbc-1e05-7789-9385-d7db12699c23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019edbbc-1e05-7789-9385-d7db12699c23" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityAbstract_019edbbc-1e05-71c2-ae38-4d499729bbef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_TemporaryEquityAbstract_019edbbc-1e05-71c2-ae38-4d499729bbef" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount_019edbbc-1e05-76de-86ee-24c7c9d19120" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TemporaryEquityAbstract_019edbbc-1e05-71c2-ae38-4d499729bbef" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount_019edbbc-1e05-76de-86ee-24c7c9d19120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ExcessStockValue_019edbbc-1e05-793d-92d7-9b46d2a06056" xlink:href="bxp-20260630.xsd#bxp_ExcessStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_bxp_ExcessStockValue_019edbbc-1e05-793d-92d7-9b46d2a06056" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_019edbbc-1e05-7878-98f5-c47b189da909" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_PreferredStockValue_019edbbc-1e05-7878-98f5-c47b189da909" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GeneralAndLimitedPartnersCapitalAccount_019edbbc-1e05-7c33-9abc-dac30466d902" xlink:href="bxp-20260630.xsd#bxp_GeneralAndLimitedPartnersCapitalAccount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_bxp_GeneralAndLimitedPartnersCapitalAccount_019edbbc-1e05-7c33-9abc-dac30466d902" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019edbbc-1e05-740f-840a-e157c7d4ea67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_CommonStockValue_019edbbc-1e05-740f-840a-e157c7d4ea67" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapital_019edbbc-1e05-77a6-ab40-7f11a77d76f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_AdditionalPaidInCapital_019edbbc-1e05-77a6-ab40-7f11a77d76f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019edbbc-1e05-72fc-bbca-89a937083ee0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019edbbc-1e05-72fc-bbca-89a937083ee0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_019edbbc-1e05-77d0-98bd-8a432a729060" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_TreasuryStockValue_019edbbc-1e05-77d0-98bd-8a432a729060" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019edbbc-1e05-7a14-ab9c-acd44d9e2243" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019edbbc-1e05-7a14-ab9c-acd44d9e2243" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019edbbc-1e05-7a89-80d6-ef25ac92f2aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_StockholdersEquity_019edbbc-1e05-7a89-80d6-ef25ac92f2aa" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapital_019edbbc-1e05-76a1-8850-04e8f4c23611" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_PartnersCapital_019edbbc-1e05-76a1-8850-04e8f4c23611" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAttributableToNoncontrollingInterest_019edbbc-1e05-7df5-bad0-617b8d0a043d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_PartnersCapitalAttributableToNoncontrollingInterest_019edbbc-1e05-7df5-bad0-617b8d0a043d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestItemsAbstract_019edbbc-1e05-7c71-b42b-9b0e69388825" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_NoncontrollingInterestItemsAbstract_019edbbc-1e05-7c71-b42b-9b0e69388825" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestInOperatingPartnerships_019edbbc-1e05-73e4-a21e-6f1ded508eff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestInOperatingPartnerships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncontrollingInterestItemsAbstract_019edbbc-1e05-7c71-b42b-9b0e69388825" xlink:to="loc_us-gaap_MinorityInterestInOperatingPartnerships_019edbbc-1e05-73e4-a21e-6f1ded508eff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestInLimitedPartnerships_019edbbc-1e05-7b41-9842-eddb242ee322" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestInLimitedPartnerships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncontrollingInterestItemsAbstract_019edbbc-1e05-7c71-b42b-9b0e69388825" xlink:to="loc_us-gaap_MinorityInterestInLimitedPartnerships_019edbbc-1e05-7b41-9842-eddb242ee322" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7875-90d4-dab85235b160" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019edbbc-1e05-7bbd-bfae-3630b9e7988b" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7875-90d4-dab85235b160" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019edbbc-1e05-74f4-8ed8-0ecb0e2d6a5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1e05-7eaa-b5a2-628164d4ba8d" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019edbbc-1e05-74f4-8ed8-0ecb0e2d6a5d" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedBalanceSheetsParenthetical"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-7a66-b60d-df9d155f8176" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-7a66-b60d-df9d155f8176" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7b5c-9857-ce62a7a8108e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-7a66-b60d-df9d155f8176" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7b5c-9857-ce62a7a8108e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7b5c-9857-ce62a7a8108e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7b5c-9857-ce62a7a8108e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7b5c-9857-ce62a7a8108e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-780f-882f-4c8bb8d687b1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7b5c-9857-ce62a7a8108e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-780f-882f-4c8bb8d687b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019edbbc-1e05-7995-b613-d632d0dbc852" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-780f-882f-4c8bb8d687b1" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019edbbc-1e05-7995-b613-d632d0dbc852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-7440-91c4-3f2f24cf71ab" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-7a66-b60d-df9d155f8176" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-7440-91c4-3f2f24cf71ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7440-91c4-3f2f24cf71ab_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7440-91c4-3f2f24cf71ab" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7440-91c4-3f2f24cf71ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-750e-a3e2-11294698ce0c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7440-91c4-3f2f24cf71ab" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-750e-a3e2-11294698ce0c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-72f4-9fb8-b256627bd9da" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-750e-a3e2-11294698ce0c" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-72f4-9fb8-b256627bd9da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019edbbc-1e05-7266-8543-93064724c316" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019edbbc-1e05-7266-8543-93064724c316" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization_019edbbc-1e05-70e0-bdce-d978ab9cba6e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAssetBeforeAccumulatedAmortization_019edbbc-1e05-70e0-bdce-d978ab9cba6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1e05-74ef-a7c1-28d72523fbc5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1e05-74ef-a7c1-28d72523fbc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7d08-b6f2-31ec991fafcc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7d08-b6f2-31ec991fafcc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7584-8087-684e33e71376" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7584-8087-684e33e71376" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_019edbbc-1e05-7545-a442-1f4b4843a49d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_AccountsReceivableNet_019edbbc-1e05-7545-a442-1f4b4843a49d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentReceivablesNet_019edbbc-1e05-73f6-963d-ba7a2b8db462" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredRentReceivablesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_DeferredRentReceivablesNet_019edbbc-1e05-73f6-963d-ba7a2b8db462" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCosts_019edbbc-1e05-7636-a481-aeafeab11940" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_DeferredCosts_019edbbc-1e05-7636-a481-aeafeab11940" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-7225-94af-a00b6d3a0256" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-7225-94af-a00b6d3a0256" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_019edbbc-1e05-7c23-9bd1-c1da65c22ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_SecuredDebt_019edbbc-1e05-7c23-9bd1-c1da65c22ef1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_019edbbc-1e05-758b-af27-fed5874f5ed9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_FinanceLeaseLiability_019edbbc-1e05-758b-af27-fed5874f5ed9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019edbbc-1e05-726a-acf5-af2246374888" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_OperatingLeaseLiability_019edbbc-1e05-726a-acf5-af2246374888" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1e05-7201-a86a-de64a5dd709d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1e05-7201-a86a-de64a5dd709d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019edbbc-1e05-7d4c-bdee-18dc2049aae5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_OtherLiabilities_019edbbc-1e05-7d4c-bdee-18dc2049aae5" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquitySharesSubscribedButUnissued_019edbbc-1e05-77f1-b2c6-14225b43a78e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquitySharesSubscribedButUnissued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_TemporaryEquitySharesSubscribedButUnissued_019edbbc-1e05-77f1-b2c6-14225b43a78e" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019edbbc-1e05-7dda-90d9-10f67be13435" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019edbbc-1e05-7dda-90d9-10f67be13435" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019edbbc-1e05-766c-81a7-e2a1722a7965" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019edbbc-1e05-766c-81a7-e2a1722a7965" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ExcessStockParOrStatedValuePerShare_019edbbc-1e05-790d-a78c-87d6951a87f6" xlink:href="bxp-20260630.xsd#bxp_ExcessStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_bxp_ExcessStockParOrStatedValuePerShare_019edbbc-1e05-790d-a78c-87d6951a87f6" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessStockSharesAuthorized_019edbbc-1e05-7720-bbaf-94d94e6c0dce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_ExcessStockSharesAuthorized_019edbbc-1e05-7720-bbaf-94d94e6c0dce" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessStockSharesOutstanding_019edbbc-1e05-7ef7-9692-cfba965a4453" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_ExcessStockSharesOutstanding_019edbbc-1e05-7ef7-9692-cfba965a4453" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessStockSharesIssued_019edbbc-1e05-770f-a660-2f13c4fb2fb8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_ExcessStockSharesIssued_019edbbc-1e05-770f-a660-2f13c4fb2fb8" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019edbbc-1e05-7018-92e8-3c2b54dc2259" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_019edbbc-1e05-7018-92e8-3c2b54dc2259" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_019edbbc-1e05-7ae0-87fb-de0487d27abc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_019edbbc-1e05-7ae0-87fb-de0487d27abc" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesIssued_019edbbc-1e05-799c-9daa-0824cb70dbdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_PreferredStockSharesIssued_019edbbc-1e05-799c-9daa-0824cb70dbdc" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019edbbc-1e05-718c-8c51-537a76570de3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019edbbc-1e05-718c-8c51-537a76570de3" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019edbbc-1e05-70b4-8f67-03355da7712e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019edbbc-1e05-70b4-8f67-03355da7712e" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019edbbc-1e05-753c-b13e-1661593a330e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019edbbc-1e05-753c-b13e-1661593a330e" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019edbbc-1e05-7bcc-8cd9-a7a1b960c6fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_CommonStockSharesIssued_019edbbc-1e05-7bcc-8cd9-a7a1b960c6fe" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-7ef6-8596-982e0791150a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-7ef6-8596-982e0791150a" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_019edbbc-1e05-7012-ab23-07bc33430484" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_us-gaap_TreasuryStockCommonShares_019edbbc-1e05-7012-ab23-07bc33430484" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsSharesOutstanding_019edbbc-1e05-7fff-86d9-d2d8448d8967" xlink:href="bxp-20260630.xsd#bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsSharesOutstanding_019edbbc-1e05-7fff-86d9-d2d8448d8967" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsLongTermIncentiveUnitsAtRedemptionValueSharesOutstanding_019edbbc-1e05-7d7b-81ed-d01ebc8014bf" xlink:href="bxp-20260630.xsd#bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsLongTermIncentiveUnitsAtRedemptionValueSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7854-a903-cca1431d032b" xlink:to="loc_bxp_NoncontrollingInterestRedeemablePartnershipUnitsCommonUnitsLongTermIncentiveUnitsAtRedemptionValueSharesOutstanding_019edbbc-1e05-7d7b-81ed-d01ebc8014bf" xlink:type="arc" order="31"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedStatementsOfOperations" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedStatementsOfOperations"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedStatementsOfOperations" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-790a-b1f2-5959ad5e9a00" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-790a-b1f2-5959ad5e9a00" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019edbbc-1e05-7668-bf71-c996e797a378" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-790a-b1f2-5959ad5e9a00" xlink:to="loc_srt_ProductOrServiceAxis_019edbbc-1e05-7668-bf71-c996e797a378" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7668-bf71-c996e797a378_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1e05-7668-bf71-c996e797a378" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7668-bf71-c996e797a378_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1e05-7668-bf71-c996e797a378" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ParkingandOtherMember_019edbbc-1e05-7995-b1d2-49b06141914f" xlink:href="bxp-20260630.xsd#bxp_ParkingandOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:to="loc_bxp_ParkingandOtherMember_019edbbc-1e05-7995-b1d2-49b06141914f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_HotelMember_019edbbc-1e05-71a2-be40-c8c57a3f3256" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_HotelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:to="loc_srt_HotelMember_019edbbc-1e05-71a2-be40-c8c57a3f3256" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementServiceMember_019edbbc-1e05-74d9-a204-f0404877897e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ManagementServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:to="loc_us-gaap_ManagementServiceMember_019edbbc-1e05-74d9-a204-f0404877897e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateOtherMember_019edbbc-1e05-7bb4-aca9-bee0f0441ded" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1e05-7b6b-9590-89a68ddb361d" xlink:to="loc_us-gaap_RealEstateOtherMember_019edbbc-1e05-7bb4-aca9-bee0f0441ded" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-790a-b1f2-5959ad5e9a00" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-72e2-8daf-b99694416584" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7a34-a4c6-c3f9821bc3d5" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-72e2-8daf-b99694416584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7f71-a8d2-9e796bde266b" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-72e2-8daf-b99694416584" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7f71-a8d2-9e796bde266b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019edbbc-1e05-7c79-9db8-708a6d5cb522" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_RevenuesAbstract_019edbbc-1e05-7c79-9db8-708a6d5cb522" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_019edbbc-1e05-7f72-920d-2fb3469b410e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019edbbc-1e05-7c79-9db8-708a6d5cb522" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_019edbbc-1e05-7f72-920d-2fb3469b410e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1e05-76ba-968a-09e0559454f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019edbbc-1e05-7c79-9db8-708a6d5cb522" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1e05-76ba-968a-09e0559454f5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019edbbc-1e05-7f2c-9a7b-ad6fce4f2a14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019edbbc-1e05-7c79-9db8-708a6d5cb522" xlink:to="loc_us-gaap_Revenues_019edbbc-1e05-7f2c-9a7b-ad6fce4f2a14" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment_019edbbc-1e05-706b-9334-d280d193958b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_DirectCostsOfLeasedAndRentedPropertyOrEquipment_019edbbc-1e05-706b-9334-d280d193958b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1e05-7647-bac6-5c9d06f52b6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1e05-7647-bac6-5c9d06f52b6c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019edbbc-1e05-77bb-845a-61ee2400cd5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019edbbc-1e05-77bb-845a-61ee2400cd5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1e05-7c2a-a09d-49dc4eba8a24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1e05-7c2a-a09d-49dc4eba8a24" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019edbbc-1e05-7319-9a27-e09250a35ffa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_DepreciationAndAmortization_019edbbc-1e05-7319-9a27-e09250a35ffa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019edbbc-1e05-78b0-ac1e-1e121d070ea7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1e05-73b3-99ba-50d9de7ad3c0" xlink:to="loc_us-gaap_CostsAndExpenses_019edbbc-1e05-78b0-ac1e-1e121d070ea7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1e05-7a20-990f-6a39ff65669e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1e05-7a20-990f-6a39ff65669e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1e05-7ced-a4af-4549c77d99a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1e05-7ced-a4af-4549c77d99a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1e05-7331-9fb2-ad88314a84f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1e05-7331-9fb2-ad88314a84f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndOtherIncome_019edbbc-1e05-7dee-b281-d7e3d6437449" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestAndOtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_InterestAndOtherIncome_019edbbc-1e05-7dee-b281-d7e3d6437449" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_019edbbc-1e05-7459-aa47-31fd5303b107" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_GainLossOnInvestments_019edbbc-1e05-7459-aa47-31fd5303b107" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingGainsLosses_019edbbc-1e05-7533-9bd9-70a391f5dfb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_OtherNonoperatingGainsLosses_019edbbc-1e05-7533-9bd9-70a391f5dfb9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1e05-716a-951d-7668f5b10e1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1e05-716a-951d-7668f5b10e1a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1e05-7124-bde3-991f1bda3ee3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1e05-7124-bde3-991f1bda3ee3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019edbbc-1e05-7c0d-bedc-509d26658579" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1e05-76b8-a9d3-e7d16feea548" xlink:to="loc_us-gaap_InterestExpense_019edbbc-1e05-7c0d-bedc-509d26658579" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1e05-712a-95dc-77ead09a866d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1e05-712a-95dc-77ead09a866d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestInNetIncomeLossOfConsolidatedEntitiesAbstract_019edbbc-1e05-7572-9ef6-88bbfd525877" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestInNetIncomeLossOfConsolidatedEntitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_MinorityInterestInNetIncomeLossOfConsolidatedEntitiesAbstract_019edbbc-1e05-7572-9ef6-88bbfd525877" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable_019edbbc-1e05-7c1d-98c6-90be8987f35a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestInNetIncomeLossOfConsolidatedEntitiesAbstract_019edbbc-1e05-7572-9ef6-88bbfd525877" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable_019edbbc-1e05-7c1d-98c6-90be8987f35a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_019edbbc-1e05-7175-936d-a51c22dd7539" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestInNetIncomeLossOfConsolidatedEntitiesAbstract_019edbbc-1e05-7572-9ef6-88bbfd525877" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_019edbbc-1e05-7175-936d-a51c22dd7539" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019edbbc-1e05-7f44-84e1-daa039ba0767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_NetIncomeLoss_019edbbc-1e05-7f44-84e1-daa039ba0767" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1e05-721e-afe8-9bce2ad86cc6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1e05-721e-afe8-9bce2ad86cc6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EarningsPerShareAfterAllocationOfUndistributedEarningsToParticipatingSecuritiesBasicDollarsPerShare_019edbbc-1e05-7445-a481-33fedc6e8098" xlink:href="bxp-20260630.xsd#bxp_EarningsPerShareAfterAllocationOfUndistributedEarningsToParticipatingSecuritiesBasicDollarsPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1e05-721e-afe8-9bce2ad86cc6" xlink:to="loc_bxp_EarningsPerShareAfterAllocationOfUndistributedEarningsToParticipatingSecuritiesBasicDollarsPerShare_019edbbc-1e05-7445-a481-33fedc6e8098" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019edbbc-1e05-7962-b71e-be97eff39e01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1e05-721e-afe8-9bce2ad86cc6" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019edbbc-1e05-7962-b71e-be97eff39e01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1e05-70c3-98aa-5a2c26c3b502" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7a17-bb80-45c0ab5978f1" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1e05-70c3-98aa-5a2c26c3b502" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019edbbc-1e05-72ca-ba2f-d3d48aae6ec1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1e05-70c3-98aa-5a2c26c3b502" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019edbbc-1e05-72ca-ba2f-d3d48aae6ec1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019edbbc-1e05-75f7-8dda-24b5cef9668c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1e05-70c3-98aa-5a2c26c3b502" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019edbbc-1e05-75f7-8dda-24b5cef9668c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedStatementsOfComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-7169-9eda-8a6bc597c431" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-7169-9eda-8a6bc597c431" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-7e22-9c94-1d00fd585780" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-7169-9eda-8a6bc597c431" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-7e22-9c94-1d00fd585780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7e22-9c94-1d00fd585780_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7e22-9c94-1d00fd585780" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7e22-9c94-1d00fd585780_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7e45-84f6-ec6114141f46" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-7e22-9c94-1d00fd585780" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7e45-84f6-ec6114141f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-72f4-857d-1e6ba37a37fe" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7e45-84f6-ec6114141f46" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-72f4-857d-1e6ba37a37fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1e05-7d65-91b2-6f43834dc6f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1e05-7d65-91b2-6f43834dc6f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019edbbc-1e05-7c5f-831c-ba90401e8c0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019edbbc-1e05-7c5f-831c-ba90401e8c0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_019edbbc-1e05-7f2f-b1c7-d76e4def53ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019edbbc-1e05-7c5f-831c-ba90401e8c0a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_019edbbc-1e05-7f2f-b1c7-d76e4def53ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_019edbbc-1e05-7312-bdca-0b516f3eaa3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019edbbc-1e05-7c5f-831c-ba90401e8c0a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_019edbbc-1e05-7312-bdca-0b516f3eaa3d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019edbbc-1e05-7214-9779-2fdca2fae750" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_019edbbc-1e05-7c5f-831c-ba90401e8c0a" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019edbbc-1e05-7214-9779-2fdca2fae750" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7722-8c78-98c16a3931d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7722-8c78-98c16a3931d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019edbbc-1e05-7370-bb7d-409af9d3a459" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019edbbc-1e05-7370-bb7d-409af9d3a459" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_019edbbc-1e05-7608-816e-c19fee211062" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_019edbbc-1e05-7608-816e-c19fee211062" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest_019edbbc-1e05-72b6-ad3c-caadfa673534" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest_019edbbc-1e05-72b6-ad3c-caadfa673534" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_019edbbc-1e05-7f80-ad4b-eef54054d36c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7726-8ed9-7d6a24937988" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_019edbbc-1e05-7f80-ad4b-eef54054d36c" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedStatementsOfEquity" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedStatementsOfEquity"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedStatementsOfEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-7e52-becc-a230d7643cd5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-7a4e-b3cf-c35b8cbfada2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7e52-becc-a230d7643cd5" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-7a4e-b3cf-c35b8cbfada2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7a94-9c8c-be15fce79f9b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-7a4e-b3cf-c35b8cbfada2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7a94-9c8c-be15fce79f9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7a94-9c8c-be15fce79f9b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7a94-9c8c-be15fce79f9b" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7a94-9c8c-be15fce79f9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7a94-9c8c-be15fce79f9b" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019edbbc-1e05-79d7-b9eb-011a88aae27a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_CommonStockMember_019edbbc-1e05-79d7-b9eb-011a88aae27a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019edbbc-1e05-7998-8856-6bec8a3531f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019edbbc-1e05-7998-8856-6bec8a3531f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019edbbc-1e05-780f-93e0-a41a170af088" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_RetainedEarningsMember_019edbbc-1e05-780f-93e0-a41a170af088" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019edbbc-1e05-7081-b139-e42a1ae22fbf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019edbbc-1e05-7081-b139-e42a1ae22fbf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019edbbc-1e05-7167-9827-2eea09291b06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019edbbc-1e05-7167-9827-2eea09291b06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1e05-74b1-ae40-03f0309fa43d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1e05-74b1-ae40-03f0309fa43d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-741b-850c-58cf69369f63" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestpropertypartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-758a-9559-ee41e944f22c" xlink:to="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-741b-850c-58cf69369f63" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7e52-becc-a230d7643cd5" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-7061-a6fb-cd8bb6494647" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-7061-a6fb-cd8bb6494647" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7179-aaa1-fbcb130acfbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7179-aaa1-fbcb130acfbc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019edbbc-1e05-76b0-829d-8670029be5fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019edbbc-1e05-76b0-829d-8670029be5fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_019edbbc-1e05-75f9-89e0-a193b257d78b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_019edbbc-1e05-75f9-89e0-a193b257d78b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EquityProfitLoss_019edbbc-1e05-777d-8921-f938ed0e7d3c" xlink:href="bxp-20260630.xsd#bxp_EquityProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_bxp_EquityProfitLoss_019edbbc-1e05-777d-8921-f938ed0e7d3c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Dividends_019edbbc-1e05-7152-8c50-50477d1f8d24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Dividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_Dividends_019edbbc-1e05-7152-8c50-50477d1f8d24" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_019edbbc-1e05-7354-97e3-a7132a0bfc0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_019edbbc-1e05-7354-97e3-a7132a0bfc0e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_019edbbc-1e05-7fd8-8770-9dd7a3a520b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_019edbbc-1e05-7fd8-8770-9dd7a3a520b3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease_019edbbc-1e05-76b2-a2db-0e17769a935a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease_019edbbc-1e05-76b2-a2db-0e17769a935a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019edbbc-1e05-73f9-8f67-880024bf3d32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_019edbbc-1e05-73f9-8f67-880024bf3d32" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-7673-a489-3d78e0b3e309" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForDerivativeInstrumentFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-7673-a489-3d78e0b3e309" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_019edbbc-1e05-75c0-aaf7-9feb71e96833" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_019edbbc-1e05-75c0-aaf7-9feb71e96833" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMinorityShareholders_019edbbc-1e05-7f3f-b794-3d93d2fd0426" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_ProceedsFromMinorityShareholders_019edbbc-1e05-7f3f-b794-3d93d2fd0426" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-7cdc-83f8-252596df4aa5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-7cdc-83f8-252596df4aa5" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019edbbc-1e05-7634-8b8f-fd9adc46f68e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019edbbc-1e05-7634-8b8f-fd9adc46f68e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeOtherNetOfTax_019edbbc-1e05-7dcb-b983-6405f4614e03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeOtherNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_us-gaap_OtherComprehensiveIncomeOtherNetOfTax_019edbbc-1e05-7dcb-b983-6405f4614e03" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollingInterestIncreaseDecreaseFromSubsidiaryEquityIssuance_019fc7d7-1af7-71f8-9c5a-0ff9e66996c9" xlink:href="bxp-20260630.xsd#bxp_NoncontrollingInterestIncreaseDecreaseFromSubsidiaryEquityIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019edbbc-1e05-745f-b5d2-b3fb8a31a0c0" xlink:to="loc_bxp_NoncontrollingInterestIncreaseDecreaseFromSubsidiaryEquityIssuance_019fc7d7-1af7-71f8-9c5a-0ff9e66996c9" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-72ac-94ca-12d64045f451" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7e52-84e5-e532fa203b53" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedStatementofCapitalandNoncontrollingInterests" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedStatementofCapitalandNoncontrollingInterests"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedStatementofCapitalandNoncontrollingInterests" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019edbbc-1e05-72dd-9e49-7eea1803b13a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_StatementTable_019edbbc-1e05-72dd-9e49-7eea1803b13a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7344-a04c-fcc69c4e3542" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-72dd-9e49-7eea1803b13a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7344-a04c-fcc69c4e3542" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7344-a04c-fcc69c4e3542_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7344-a04c-fcc69c4e3542" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7344-a04c-fcc69c4e3542_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7344-a04c-fcc69c4e3542" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-71c6-9f11-92f2448458ab" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-71c6-9f11-92f2448458ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019edbbc-1e05-7691-a9fb-81538f462b84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019edbbc-1e05-7691-a9fb-81538f462b84" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-7f41-a4a6-49b4a6f00886" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestpropertypartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:to="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-7f41-a4a6-49b4a6f00886" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CapitalMember_019edbbc-1e05-7d85-891b-7d8ee3996fb5" xlink:href="bxp-20260630.xsd#bxp_CapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:to="loc_bxp_CapitalMember_019edbbc-1e05-7d85-891b-7d8ee3996fb5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestRedeemablepartnershipunitsMember_019edbbc-1e05-77af-9ac8-1e7afd3876a0" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestRedeemablepartnershipunitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7f3d-9237-622f24f9f17e" xlink:to="loc_bxp_NoncontrollinginterestRedeemablepartnershipunitsMember_019edbbc-1e05-77af-9ac8-1e7afd3876a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-71bd-9021-6d6597bbf1c8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019edbbc-1e05-72dd-9e49-7eea1803b13a" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-71bd-9021-6d6597bbf1c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-71bd-9021-6d6597bbf1c8_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-71bd-9021-6d6597bbf1c8" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-71bd-9021-6d6597bbf1c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7702-b77c-44470a62c929" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-71bd-9021-6d6597bbf1c8" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7702-b77c-44470a62c929" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_019edbbc-1e05-76fd-a60f-a6e067df4d8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7702-b77c-44470a62c929" xlink:to="loc_us-gaap_GeneralPartnerMember_019edbbc-1e05-76fd-a60f-a6e067df4d8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_019edbbc-1e05-7778-94f8-eb590a5e9be4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7702-b77c-44470a62c929" xlink:to="loc_us-gaap_LimitedPartnerMember_019edbbc-1e05-7778-94f8-eb590a5e9be4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-729b-b9e7-db6815c8fe36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1e05-729b-b9e7-db6815c8fe36" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7495-86c7-96f1d1da2227" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalIncludingPortionAttributableToNoncontrollingInterest_019edbbc-1e05-7495-86c7-96f1d1da2227" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019edbbc-1e05-7489-90fd-2f2884d72a5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019edbbc-1e05-7489-90fd-2f2884d72a5b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountContributions_019edbbc-1e05-7885-a9ec-9e378499ee36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAccountContributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalAccountContributions_019edbbc-1e05-7885-a9ec-9e378499ee36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NetIncomeAllocableToGeneralAndLimitedPartnerUnits_019edbbc-1e05-75dc-bed5-c590049a8935" xlink:href="bxp-20260630.xsd#bxp_NetIncomeAllocableToGeneralAndLimitedPartnerUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_bxp_NetIncomeAllocableToGeneralAndLimitedPartnerUnits_019edbbc-1e05-75dc-bed5-c590049a8935" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountDistributions_019edbbc-1e05-7238-b4e2-6e15487197ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAccountDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalAccountDistributions_019edbbc-1e05-7238-b4e2-6e15487197ac" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountDeferredCompensation_019edbbc-1e05-7f8f-a7a8-6460382235df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAccountDeferredCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalAccountDeferredCompensation_019edbbc-1e05-7f8f-a7a8-6460382235df" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019edbbc-1e05-7ef6-9781-b289ff412ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019edbbc-1e05-7ef6-9781-b289ff412ac8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountExchangesAndConversions_019edbbc-1e05-7ae4-8ace-27dd5dbd3091" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAccountExchangesAndConversions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalAccountExchangesAndConversions_019edbbc-1e05-7ae4-8ace-27dd5dbd3091" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnersCapitalAccountRedemptions_019edbbc-1e05-7c73-a16c-d699d64f672b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnersCapitalAccountRedemptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PartnersCapitalAccountRedemptions_019edbbc-1e05-7c73-a16c-d699d64f672b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019edbbc-1e05-71cc-b3b5-c292444a5fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_019edbbc-1e05-71cc-b3b5-c292444a5fc0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeOtherNetOfTax_019edbbc-1e05-786c-9e3b-aafd925c67ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeOtherNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_OtherComprehensiveIncomeOtherNetOfTax_019edbbc-1e05-786c-9e3b-aafd925c67ac" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-75a3-b231-1491ad6813f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForDerivativeInstrumentFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-75a3-b231-1491ad6813f2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_019edbbc-1e05-7a20-ab73-45dbcccaaa89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PaymentsToAcquireAdditionalInterestInSubsidiaries_019edbbc-1e05-7a20-ab73-45dbcccaaa89" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMinorityShareholders_019edbbc-1e05-703d-a628-4e7574f8f35f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_ProceedsFromMinorityShareholders_019edbbc-1e05-703d-a628-4e7574f8f35f" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-794c-b59f-f3d8a5250f90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-7772-8ae1-100c12f6d662" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-794c-b59f-f3d8a5250f90" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="simple" xlink:href="bxp-20260630.xsd#ConsolidatedStatementsOfCashFlows"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1e05-7183-bc90-7498d3fa574b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_dei_EntitiesTable_019edbbc-1e05-7183-bc90-7498d3fa574b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-74e8-b4f3-ed8baf9129c1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7183-bc90-7498d3fa574b" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-74e8-b4f3-ed8baf9129c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-74e8-b4f3-ed8baf9129c1_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-74e8-b4f3-ed8baf9129c1" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-74e8-b4f3-ed8baf9129c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7b70-a840-0055ff99e0fe" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-74e8-b4f3-ed8baf9129c1" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7b70-a840-0055ff99e0fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-70cb-90d6-a5f57817c91f" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7b70-a840-0055ff99e0fe" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-70cb-90d6-a5f57817c91f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-7833-b720-f1bdaf84091d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7183-bc90-7498d3fa574b" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-7833-b720-f1bdaf84091d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7833-b720-f1bdaf84091d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-7833-b720-f1bdaf84091d" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7833-b720-f1bdaf84091d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7836-814b-b3c9d1adaae3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-7833-b720-f1bdaf84091d" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7836-814b-b3c9d1adaae3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashMember_019edbbc-1e05-774f-910e-e3ab53143065" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7836-814b-b3c9d1adaae3" xlink:to="loc_us-gaap_CashMember_019edbbc-1e05-774f-910e-e3ab53143065" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7755-8c8f-94663f918406" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7183-bc90-7498d3fa574b" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7755-8c8f-94663f918406" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7755-8c8f-94663f918406_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7755-8c8f-94663f918406" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7755-8c8f-94663f918406_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7879-af9a-1a5ce6b38553" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7755-8c8f-94663f918406" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7879-af9a-1a5ce6b38553" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoOneZeroZeroMStreetMember_019edbbc-1e05-71f9-a015-4a9bf7a14d4a" xlink:href="bxp-20260630.xsd#bxp_TwoOneZeroZeroMStreetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7879-af9a-1a5ce6b38553" xlink:to="loc_bxp_TwoOneZeroZeroMStreetMember_019edbbc-1e05-71f9-a015-4a9bf7a14d4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1e05-7017-8907-d0149718b3ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1e05-7017-8907-d0149718b3ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-795a-9cb6-a42cb6694e31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-795a-9cb6-a42cb6694e31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-795a-9cb6-a42cb6694e31" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_019edbbc-1e05-787b-94f1-f482452bcaff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_019edbbc-1e05-787b-94f1-f482452bcaff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019fc31f-075a-7f99-916c-3317642eb85d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019fc31f-075a-7f99-916c-3317642eb85d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019edbbc-1e05-7cdf-a41b-1cd275862f89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_019edbbc-1e05-7cdf-a41b-1cd275862f89" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AmortizationOfSalesTypeLease_019edbbc-1e05-774e-8393-a8ba43e048a1" xlink:href="bxp-20260630.xsd#bxp_AmortizationOfSalesTypeLease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_bxp_AmortizationOfSalesTypeLease_019edbbc-1e05-774e-8393-a8ba43e048a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_019edbbc-1e05-72b3-9f38-dfa0fd0c969c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_ShareBasedCompensation_019edbbc-1e05-72b3-9f38-dfa0fd0c969c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1e05-7fa8-bffb-8a5c47ac667b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1e05-7fa8-bffb-8a5c47ac667b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_019edbbc-1e05-7c82-ac4d-8812cefacc48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentDividendsOrDistributions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_EquityMethodInvestmentDividendsOrDistributions_019edbbc-1e05-7c82-ac4d-8812cefacc48" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfInvestments_019edbbc-1e05-71d8-a14d-b5d68e599d9a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnSaleOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_GainLossOnSaleOfInvestments_019edbbc-1e05-71d8-a14d-b5d68e599d9a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForLoanLeaseAndOtherLosses_019edbbc-1e05-766b-afec-03f6704d1117" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProvisionForLoanLeaseAndOtherLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_ProvisionForLoanLeaseAndOtherLosses_019edbbc-1e05-766b-afec-03f6704d1117" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaidInKindInterest_019edbbc-1e05-7eee-95a8-67521a6db185" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaidInKindInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_PaidInKindInterest_019edbbc-1e05-7eee-95a8-67521a6db185" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1e05-76a9-89af-092f9daf1451" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1e05-76a9-89af-092f9daf1451" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1e05-7cc7-863a-bac4bd7d4585" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1e05-7cc7-863a-bac4bd7d4585" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1e05-7644-b49f-02b78a361f5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1e05-7644-b49f-02b78a361f5d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingGainsLosses_019edbbc-1e05-7c89-9e1d-98b6f6e5ebd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_NonoperatingGainsLosses_019edbbc-1e05-7c89-9e1d-98b6f6e5ebd1" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019edbbc-1e05-7e49-8a56-bac828d4bda2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_019edbbc-1e05-7e49-8a56-bac828d4bda2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StraightLineRent_019edbbc-1e05-7b8a-968d-5d26e3a83354" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StraightLineRent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_StraightLineRent_019edbbc-1e05-7b8a-968d-5d26e3a83354" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019edbbc-1e05-7c7e-aae8-18ea48ea08f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_019edbbc-1e05-7c7e-aae8-18ea48ea08f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_019edbbc-1e05-7375-94d8-c69232e19068" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet_019edbbc-1e05-7375-94d8-c69232e19068" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019edbbc-1e05-7fe6-9dbb-8d7c0412b9ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_019edbbc-1e05-7fe6-9dbb-8d7c0412b9ad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019edbbc-1e05-7f4e-9428-b813d15e5f58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInInterestPayableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInInterestPayableNet_019edbbc-1e05-7f4e-9428-b813d15e5f58" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019edbbc-1e05-7bfa-acf6-42f35ece91de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_019edbbc-1e05-7bfa-acf6-42f35ece91de" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019edbbc-1e05-76fa-986c-f99e868dc8b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_019edbbc-1e05-7bb3-a268-ff2c8910edf5" xlink:to="loc_us-gaap_LeaseCost_019edbbc-1e05-76fa-986c-f99e868dc8b6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities_019edbbc-1e05-707a-8642-9968c2ae66a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-70d3-8249-bb41e96968b8" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivities_019edbbc-1e05-707a-8642-9968c2ae66a1" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019edbbc-1e05-75d7-ad01-cd3b6daab36d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_019edbbc-1e05-795a-9cb6-a42cb6694e31" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_019edbbc-1e05-75d7-ad01-cd3b6daab36d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireCommercialRealEstate_019edbbc-1e05-7084-b811-992adc32cff5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireCommercialRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsToAcquireCommercialRealEstate_019edbbc-1e05-7084-b811-992adc32cff5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireOtherProductiveAssets_019edbbc-1e05-717c-90e1-cf58ff82a880" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireOtherProductiveAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsToAcquireOtherProductiveAssets_019edbbc-1e05-717c-90e1-cf58ff82a880" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForCapitalImprovements_019edbbc-1e05-726d-b1ce-041bf2976450" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForCapitalImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsForCapitalImprovements_019edbbc-1e05-726d-b1ce-041bf2976450" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForTenantImprovements_019edbbc-1e05-7c71-9220-985274f8f10e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForTenantImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsForTenantImprovements_019edbbc-1e05-7c71-9220-985274f8f10e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures_019edbbc-1e05-7166-a4b3-9c44a0f691d7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures_019edbbc-1e05-7166-a4b3-9c44a0f691d7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019edbbc-1e05-7f51-abb1-fc2fdf8a16df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_019edbbc-1e05-7f51-abb1-fc2fdf8a16df" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019edbbc-1e05-78f3-83a1-4f49ec2c1b45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019edbbc-1e05-78f3-83a1-4f49ec2c1b45" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_019edbbc-1e05-7b9f-8368-8e3f918b947e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_019edbbc-1e05-7b9f-8368-8e3f918b947e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1e05-75b0-965c-d6ec11ccdeba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1e05-75b0-965c-d6ec11ccdeba" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019edbbc-1e05-71c3-901d-4a1fe05e9690" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019edbbc-1e05-71c3-901d-4a1fe05e9690" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OriginationOfNotesReceivableFromRelatedParties_019edbbc-1e05-745f-87b1-58fbf8c0cf59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OriginationOfNotesReceivableFromRelatedParties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_OriginationOfNotesReceivableFromRelatedParties_019edbbc-1e05-745f-87b1-58fbf8c0cf59" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromMortgageDeposits_019edbbc-1e05-79c9-9e42-3fca57ff956d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromMortgageDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_ProceedsFromMortgageDeposits_019edbbc-1e05-79c9-9e42-3fca57ff956d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromInvestments_019edbbc-1e05-7dea-bec7-90c5974f54f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_PaymentsForProceedsFromInvestments_019edbbc-1e05-7dea-bec7-90c5974f54f2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019edbbc-1e05-74e5-865b-1844bb578433" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_019edbbc-1e05-7154-a101-a22baab48501" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_019edbbc-1e05-74e5-865b-1844bb578433" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSecuredNotesPayable_019edbbc-1e05-75cf-9162-a0018f0fec1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSecuredNotesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromSecuredNotesPayable_019edbbc-1e05-75cf-9162-a0018f0fec1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfSecuredDebt_019edbbc-1e05-749e-9bb5-431b6a765f27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfSecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_RepaymentsOfSecuredDebt_019edbbc-1e05-749e-9bb5-431b6a765f27" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfUnsecuredDebt_019edbbc-1e05-7fec-98f7-67375952f0a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfUnsecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfUnsecuredDebt_019edbbc-1e05-7fec-98f7-67375952f0a8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfUnsecuredDebt_019edbbc-1e05-7314-9f9b-5df9262ca0c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfUnsecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_RepaymentsOfUnsecuredDebt_019edbbc-1e05-7314-9f9b-5df9262ca0c2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromConvertibleDebt_019edbbc-1e05-7704-9b9b-e755334165e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromConvertibleDebt_019edbbc-1e05-7704-9b9b-e755334165e9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_019edbbc-1e05-70f6-80fc-a9eea692f4a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_019edbbc-1e05-70f6-80fc-a9eea692f4a0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_019edbbc-1e05-711b-a8f5-f1f992d7a1b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_019edbbc-1e05-711b-a8f5-f1f992d7a1b9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromOtherDebt_019edbbc-1e05-75f4-aa00-7519a6bfa839" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromOtherDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromOtherDebt_019edbbc-1e05-75f4-aa00-7519a6bfa839" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfOtherDebt_019edbbc-1e05-7342-be74-58c749741616" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfOtherDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_RepaymentsOfOtherDebt_019edbbc-1e05-7342-be74-58c749741616" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_019edbbc-1e05-7cbb-a906-01b30c237eea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_019edbbc-1e05-7cbb-a906-01b30c237eea" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommercialPaper_019edbbc-1e05-7e86-9b8c-ccf030b426a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfCommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommercialPaper_019edbbc-1e05-7e86-9b8c-ccf030b426a6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfCommercialPaper_019edbbc-1e05-7b03-b18c-8c97b981ba1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfCommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_RepaymentsOfCommercialPaper_019edbbc-1e05-7b03-b18c-8c97b981ba1e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfFinancingCosts_019edbbc-1e05-71d5-b53b-9d42aee6913a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_PaymentsOfFinancingCosts_019edbbc-1e05-71d5-b53b-9d42aee6913a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-7f84-bb11-d471732e4445" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForDerivativeInstrumentFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_PaymentsForDerivativeInstrumentFinancingActivities_019edbbc-1e05-7f84-bb11-d471732e4445" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019edbbc-1e05-7b39-bc6c-e5713f2f9ecc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromIssuanceOrSaleOfEquity_019edbbc-1e05-7b39-bc6c-e5713f2f9ecc" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividends_019edbbc-1e05-7853-9b85-d2e715739bce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfDividends"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_PaymentsOfDividends_019edbbc-1e05-7853-9b85-d2e715739bce" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ProceedsFromNoncontrollingInterestCashPortion_019edbbc-1e05-75f9-ae02-9a246811295c" xlink:href="bxp-20260630.xsd#bxp_ProceedsFromNoncontrollingInterestCashPortion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_bxp_ProceedsFromNoncontrollingInterestCashPortion_019edbbc-1e05-75f9-ae02-9a246811295c" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-733a-884c-de376d20a8de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToMinorityShareholders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_PaymentsToMinorityShareholders_019edbbc-1e05-733a-884c-de376d20a8de" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019edbbc-1e05-7a97-890f-9ffa2a331887" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_019edbbc-1e05-7a97-890f-9ffa2a331887" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019edbbc-1e05-7310-b6e6-62d6a7918b33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_019edbbc-1e05-7caa-9f26-13cca3360fc4" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_019edbbc-1e05-7310-b6e6-62d6a7918b33" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019edbbc-1e05-7d3a-92d8-3903d7714df1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_019edbbc-1e05-7d3a-92d8-3903d7714df1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019edbbc-1e05-7572-92d3-d2f38d7d3d60" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019edbbc-1e05-7572-92d3-d2f38d7d3d60" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_019edbbc-1e05-79c4-8a38-81b305a385d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_019edbbc-1e05-79f3-9ac5-b36e7450940a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_019edbbc-1e05-79f3-9ac5-b36e7450940a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7237-9623-859676ef5cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_019edbbc-1e05-79f3-9ac5-b36e7450940a" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7237-9623-859676ef5cc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7d7b-9cb3-a23c2d74955e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsAbstract_019edbbc-1e05-79f3-9ac5-b36e7450940a" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7d7b-9cb3-a23c2d74955e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-78ae-82af-7f57a70a6be7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_019edbbc-1e05-7d8f-87ac-ece661c7abfd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_019edbbc-1e05-7322-93b5-23108815370a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_019edbbc-1e05-7322-93b5-23108815370a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_019edbbc-1e05-7f99-a0e7-818c6ae5f8c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_019edbbc-1e05-7322-93b5-23108815370a" xlink:to="loc_us-gaap_InterestPaidNet_019edbbc-1e05-7f99-a0e7-818c6ae5f8c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestCostsCapitalized_019edbbc-1e05-7cbe-86f4-9c38d467b3e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestCostsCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_019edbbc-1e05-7322-93b5-23108815370a" xlink:to="loc_us-gaap_InterestCostsCapitalized_019edbbc-1e05-7cbe-86f4-9c38d467b3e0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1e05-792f-9242-4ac75a223591" xlink:to="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Writeoffoffullydepreciatedrealestate_019edbbc-1e05-7ff9-8302-acbb90178a83" xlink:href="bxp-20260630.xsd#bxp_Writeoffoffullydepreciatedrealestate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_Writeoffoffullydepreciatedrealestate_019edbbc-1e05-7ff9-8302-acbb90178a83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ChangeInRealEstateIncludedInAccountsPayableAndAccruedExpenses_019edbbc-1e05-72bf-90e6-45f35f3c30fd" xlink:href="bxp-20260630.xsd#bxp_ChangeInRealEstateIncludedInAccountsPayableAndAccruedExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_ChangeInRealEstateIncludedInAccountsPayableAndAccruedExpenses_019edbbc-1e05-72bf-90e6-45f35f3c30fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019edbbc-1e05-7998-96f6-6cba38716f47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_019edbbc-1e05-7998-96f6-6cba38716f47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability_019edbbc-1e05-7e40-8657-9f93099dd12b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability_019edbbc-1e05-7e40-8657-9f93099dd12b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FinanceLeaseLiabilityReversalFromReAssessment_019edbbc-1e05-70e9-82c3-9a830a2e28a8" xlink:href="bxp-20260630.xsd#bxp_FinanceLeaseLiabilityReversalFromReAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_FinanceLeaseLiabilityReversalFromReAssessment_019edbbc-1e05-70e9-82c3-9a830a2e28a8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FinanceLeaseRightOfUseAssetReversalFromReAssessment_019edbbc-1e05-7056-a439-35e72a0db3e1" xlink:href="bxp-20260630.xsd#bxp_FinanceLeaseRightOfUseAssetReversalFromReAssessment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_FinanceLeaseRightOfUseAssetReversalFromReAssessment_019edbbc-1e05-7056-a439-35e72a0db3e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NonCashContributionsFromNoncontrollingInterestsInPropertyPartnershipsNet_019edbbc-1e05-74b3-95f3-e59a0264f5fb" xlink:href="bxp-20260630.xsd#bxp_NonCashContributionsFromNoncontrollingInterestsInPropertyPartnershipsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_NonCashContributionsFromNoncontrollingInterestsInPropertyPartnershipsNet_019edbbc-1e05-74b3-95f3-e59a0264f5fb" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CapitalizedOperatingLeaseCosts_019edbbc-1e05-71d7-824b-35051bc3e61e" xlink:href="bxp-20260630.xsd#bxp_CapitalizedOperatingLeaseCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_CapitalizedOperatingLeaseCosts_019edbbc-1e05-71d7-824b-35051bc3e61e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ConstructionInProgressFromPrepaidExpensesAndOtherAssets_019edbbc-1e05-7a54-9ba5-1f1853afe7fb" xlink:href="bxp-20260630.xsd#bxp_ConstructionInProgressFromPrepaidExpensesAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_ConstructionInProgressFromPrepaidExpensesAndOtherAssets_019edbbc-1e05-7a54-9ba5-1f1853afe7fb" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InvestmentInUnconsolidatedJointVenturesEliminatedUponConsolidation_019edbbc-1e05-7b9c-8cb3-c85902fece28" xlink:href="bxp-20260630.xsd#bxp_InvestmentInUnconsolidatedJointVenturesEliminatedUponConsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_InvestmentInUnconsolidatedJointVenturesEliminatedUponConsolidation_019edbbc-1e05-7b9c-8cb3-c85902fece28" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansAssumed1_019edbbc-1e05-7dcc-98ef-b0cb23c32084" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansAssumed1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_LoansAssumed1_019edbbc-1e05-7dcc-98ef-b0cb23c32084" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_019edbbc-1e05-73e8-a920-5b78483e656a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_DebtConversionConvertedInstrumentAmount1_019edbbc-1e05-73e8-a920-5b78483e656a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransferToInvestments_019edbbc-1e05-709a-9899-a1766b28ce70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransferToInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_TransferToInvestments_019edbbc-1e05-709a-9899-a1766b28ce70" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InterestRateSwapsRecordedUponConsolidation_019edbbc-1e05-7805-ae17-3f97ed727c19" xlink:href="bxp-20260630.xsd#bxp_InterestRateSwapsRecordedUponConsolidation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_InterestRateSwapsRecordedUponConsolidation_019edbbc-1e05-7805-ae17-3f97ed727c19" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ConstructionInProgressNetDeconsolidated_019edbbc-1e05-7ee3-af91-55617a20d1b4" xlink:href="bxp-20260630.xsd#bxp_ConstructionInProgressNetDeconsolidated"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_ConstructionInProgressNetDeconsolidated_019edbbc-1e05-7ee3-af91-55617a20d1b4" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InvestmentInUnconsolidatedJointVenturesFundedByRealEstateContributed_019edbbc-1e05-7930-8ad3-0e34622694c3" xlink:href="bxp-20260630.xsd#bxp_InvestmentInUnconsolidatedJointVenturesFundedByRealEstateContributed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_InvestmentInUnconsolidatedJointVenturesFundedByRealEstateContributed_019edbbc-1e05-7930-8ad3-0e34622694c3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019edbbc-1e05-7b63-8cc8-7e048816e7d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_us-gaap_DividendsPayableCurrentAndNoncurrent_019edbbc-1e05-7b63-8cc8-7e048816e7d6" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ConversionsOfNoncontrollingInterestsToStockholdersEquity_019edbbc-1e05-7853-8f52-2a7fec90c1a3" xlink:href="bxp-20260630.xsd#bxp_ConversionsOfNoncontrollingInterestsToStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_ConversionsOfNoncontrollingInterestsToStockholdersEquity_019edbbc-1e05-7853-8f52-2a7fec90c1a3" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_IssuanceOfRestrictedSecuritiesToEmployeesAndDirectors_019edbbc-1e05-74f4-b046-8051e164672c" xlink:href="bxp-20260630.xsd#bxp_IssuanceOfRestrictedSecuritiesToEmployeesAndDirectors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_019edbbc-1e05-7291-a5c0-e4bd03e06658" xlink:to="loc_bxp_IssuanceOfRestrictedSecuritiesToEmployeesAndDirectors_019edbbc-1e05-74f4-b046-8051e164672c" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#SummaryOfSignificantAccountingPoliciesTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:href="bxp-20260630.xsd#bxp_SummaryOfSignificantAccountingPoliciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SummaryOfSignificantAccountingPoliciesTable_019edbbc-1e05-7e32-ac69-b5a0bfdb231e" xlink:href="bxp-20260630.xsd#bxp_SummaryOfSignificantAccountingPoliciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_bxp_SummaryOfSignificantAccountingPoliciesTable_019edbbc-1e05-7e32-ac69-b5a0bfdb231e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7410-82ce-10a703b68dd2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesTable_019edbbc-1e05-7e32-ac69-b5a0bfdb231e" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7410-82ce-10a703b68dd2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7410-82ce-10a703b68dd2_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7410-82ce-10a703b68dd2" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7410-82ce-10a703b68dd2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7825-9e82-bc3e2784afcb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-7410-82ce-10a703b68dd2" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7825-9e82-bc3e2784afcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_019edbbc-1e05-775b-b923-6f3f7585c3f1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7825-9e82-bc3e2784afcb" xlink:to="loc_srt_SubsidiariesMember_019edbbc-1e05-775b-b923-6f3f7585c3f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTextBlock_019edbbc-1e05-7989-9b00-cc7a9d72a88b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTextBlock_019edbbc-1e05-7989-9b00-cc7a9d72a88b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock_019edbbc-1e05-7d57-9d13-b10193d877ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_us-gaap_ScheduleofFiniteLivedIntangibleAssetsFutureAmortizationExpenseTableTextBlock_019edbbc-1e05-7d57-9d13-b10193d877ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTextBlock_019edbbc-1e05-7a02-92f6-5d7d9b805d73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByBalanceSheetGroupingTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTextBlock_019edbbc-1e05-7a02-92f6-5d7d9b805d73" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDerivativeAssetsAtFairValueTableTextBlock_019edbbc-1e05-7fa9-b4f9-8b22c1d1d9cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDerivativeAssetsAtFairValueTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_us-gaap_ScheduleOfDerivativeAssetsAtFairValueTableTextBlock_019edbbc-1e05-7fa9-b4f9-8b22c1d1d9cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RealEstateInvestmentTrustDistributionTaxStatusTableTextBlock_019edbbc-1e05-7992-802f-8cee91ba0a86" xlink:href="bxp-20260630.xsd#bxp_RealEstateInvestmentTrustDistributionTaxStatusTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-746f-99c7-3188b6d399b9" xlink:to="loc_bxp_RealEstateInvestmentTrustDistributionTaxStatusTableTextBlock_019edbbc-1e05-7992-802f-8cee91ba0a86" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/RealEstateTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#RealEstateTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/RealEstateTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7a77-a3bb-d25c3708ea7d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7a77-a3bb-d25c3708ea7d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-76db-af2c-ac2d840f403c" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7a77-a3bb-d25c3708ea7d" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-76db-af2c-ac2d840f403c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-76db-af2c-ac2d840f403c_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-76db-af2c-ac2d840f403c" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-76db-af2c-ac2d840f403c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-77a4-b672-fbf57f192636" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-76db-af2c-ac2d840f403c" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-77a4-b672-fbf57f192636" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7567-99cb-82651943575c" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-77a4-b672-fbf57f192636" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7567-99cb-82651943575c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsIncomeStatementBalanceSheetAndAdditionalDisclosuresTextBlock_019edbbc-1ec9-7e97-96f8-49b37df6d6de" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsIncomeStatementBalanceSheetAndAdditionalDisclosuresTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:to="loc_us-gaap_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsIncomeStatementBalanceSheetAndAdditionalDisclosuresTextBlock_019edbbc-1ec9-7e97-96f8-49b37df6d6de" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock_019edbbc-1ec9-777d-908c-5b14b5ecd860" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:to="loc_us-gaap_ScheduleOfPropertySubjectToOrAvailableForOperatingLeaseTextBlock_019edbbc-1ec9-777d-908c-5b14b5ecd860" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisclosureOfLongLivedAssetsHeldForSaleTextBlock_019fb887-629a-7f04-8e9c-dae9f2ce1af0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisclosureOfLongLivedAssetsHeldForSaleTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:to="loc_us-gaap_DisclosureOfLongLivedAssetsHeldForSaleTextBlock_019fb887-629a-7f04-8e9c-dae9f2ce1af0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RealizedGainLossOnSaleOfRealEstateTableTextBlock_019edbbc-1ec9-7448-be70-0ff861fc521a" xlink:href="bxp-20260630.xsd#bxp_RealizedGainLossOnSaleOfRealEstateTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7832-a77e-4112e95c252f" xlink:to="loc_bxp_RealizedGainLossOnSaleOfRealEstateTableTextBlock_019edbbc-1ec9-7448-be70-0ff861fc521a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/LeasesTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#LeasesTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/LeasesTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019edbbc-1ec9-7afb-a4a4-a92c3a67e926" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019edbbc-1ec9-78b1-830e-cab1a0b34cb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019edbbc-1ec9-7afb-a4a4-a92c3a67e926" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019edbbc-1ec9-78b1-830e-cab1a0b34cb5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCostTableTextBlock_019edbbc-1ec9-78e1-b2c1-3417e060527b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LeaseCostTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019edbbc-1ec9-7afb-a4a4-a92c3a67e926" xlink:to="loc_us-gaap_LeaseCostTableTextBlock_019edbbc-1ec9-78e1-b2c1-3417e060527b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_019edbbc-1ec9-73f1-b6f6-7ca3ba2e556e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019edbbc-1ec9-7afb-a4a4-a92c3a67e926" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_019edbbc-1ec9-73f1-b6f6-7ca3ba2e556e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock_019edbbc-1ec9-7a27-9862-2aa3e16b234e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019edbbc-1ec9-7afb-a4a4-a92c3a67e926" xlink:to="loc_us-gaap_FinanceLeaseLiabilityMaturityTableTextBlock_019edbbc-1ec9-7a27-9862-2aa3e16b234e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-73c0-a086-c7193621586f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-73c0-a086-c7193621586f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentsTextBlock_019edbbc-1ec9-76b8-ade8-db68bcb9df74" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentsTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:to="loc_us-gaap_EquityMethodInvestmentsTextBlock_019edbbc-1ec9-76b8-ade8-db68bcb9df74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ScheduleOfBalanceSheetsOfUnconsolidatedJointVenturesTextBlock_019edbbc-1ec9-74d7-8a74-a163b770d7e3" xlink:href="bxp-20260630.xsd#bxp_ScheduleOfBalanceSheetsOfUnconsolidatedJointVenturesTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:to="loc_bxp_ScheduleOfBalanceSheetsOfUnconsolidatedJointVenturesTextBlock_019edbbc-1ec9-74d7-8a74-a163b770d7e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ScheduleOfStatementsOfOperationsOfUnconsolidatedJointVenturesTextBock_019edbbc-1ec9-7943-beec-4485035c2d0d" xlink:href="bxp-20260630.xsd#bxp_ScheduleOfStatementsOfOperationsOfUnconsolidatedJointVenturesTextBock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:to="loc_bxp_ScheduleOfStatementsOfOperationsOfUnconsolidatedJointVenturesTextBock_019edbbc-1ec9-7943-beec-4485035c2d0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EquityMethodInvestmentRealizedGainLossOnDisposalTableTextBlock_019edbbc-1ec9-79b2-b6c7-60f4910f5c4c" xlink:href="bxp-20260630.xsd#bxp_EquityMethodInvestmentRealizedGainLossOnDisposalTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7b76-84e1-7c89355edbc3" xlink:to="loc_bxp_EquityMethodInvestmentRealizedGainLossOnDisposalTableTextBlock_019edbbc-1ec9-79b2-b6c7-60f4910f5c4c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/NoncontrollingInterestsTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#NoncontrollingInterestsTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/NoncontrollingInterestsTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7e75-88a2-6373f899573b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_019edbbc-1fab-7641-b771-64b0b2e32a70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7e75-88a2-6373f899573b" xlink:to="loc_us-gaap_MinorityInterestTable_019edbbc-1fab-7641-b771-64b0b2e32a70" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7a18-a8b3-5de25d8cee0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_019edbbc-1fab-7641-b771-64b0b2e32a70" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7a18-a8b3-5de25d8cee0d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7a18-a8b3-5de25d8cee0d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7a18-a8b3-5de25d8cee0d" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7a18-a8b3-5de25d8cee0d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-72ca-8463-30ec5fa3073e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7a18-a8b3-5de25d8cee0d" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-72ca-8463-30ec5fa3073e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1fab-79be-a845-dbc72f9b1ffc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-72ca-8463-30ec5fa3073e" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1fab-79be-a845-dbc72f9b1ffc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ScheduleOfNoncontrollingInterestTableTextBlock_019edbbc-1fab-78bd-acac-6ebc8670d484" xlink:href="bxp-20260630.xsd#bxp_ScheduleOfNoncontrollingInterestTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7e75-88a2-6373f899573b" xlink:to="loc_bxp_ScheduleOfNoncontrollingInterestTableTextBlock_019edbbc-1fab-78bd-acac-6ebc8670d484" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock_019edbbc-1fab-7283-a9cd-703f55ab8c22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7e75-88a2-6373f899573b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardPerformanceBasedUnitsVestedAndExpectedToVestTableTextBlock_019edbbc-1fab-7283-a9cd-703f55ab8c22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsDeclaredTableTextBlock_019edbbc-1fab-702b-b7a3-f6a023ea39c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsDeclaredTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7e75-88a2-6373f899573b" xlink:to="loc_us-gaap_DividendsDeclaredTableTextBlock_019edbbc-1fab-702b-b7a3-f6a023ea39c1" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockholdersEquityPartnersCapitalTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockholdersEquityPartnersCapitalTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockholdersEquityPartnersCapitalTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-7952-a222-ae379cbeb89c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019edbbc-1fab-7b43-b44e-03d591d581df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-7952-a222-ae379cbeb89c" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019edbbc-1fab-7b43-b44e-03d591d581df" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsDeclaredTableTextBlock_019edbbc-1fab-70f3-a164-bb11cef645f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsDeclaredTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-7952-a222-ae379cbeb89c" xlink:to="loc_us-gaap_DividendsDeclaredTableTextBlock_019edbbc-1fab-70f3-a164-bb11cef645f5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/EarningsPerShareCommonUnitTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#EarningsPerShareCommonUnitTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/EarningsPerShareCommonUnitTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019edbbc-1fab-70bf-b842-ecc4546421d9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1fab-7f07-957b-23892b729596" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_019edbbc-1fab-70bf-b842-ecc4546421d9" xlink:to="loc_dei_EntitiesTable_019edbbc-1fab-7f07-957b-23892b729596" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7004-b6ca-aa9f672cb701" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1fab-7f07-957b-23892b729596" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7004-b6ca-aa9f672cb701" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7004-b6ca-aa9f672cb701_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7004-b6ca-aa9f672cb701" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7004-b6ca-aa9f672cb701_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7b0e-8928-02e1337e1295" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7004-b6ca-aa9f672cb701" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7b0e-8928-02e1337e1295" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7184-8a3b-65f95732d881" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7b0e-8928-02e1337e1295" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7184-8a3b-65f95732d881" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_019edbbc-1fab-766a-828c-cda90badcc2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019edbbc-1fab-70bf-b842-ecc4546421d9" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_019edbbc-1fab-766a-828c-cda90badcc2a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockOptionandIncentivePlanTables" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockOptionandIncentivePlanTables"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockOptionandIncentivePlanTables" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-7194-89b6-fb7cea446469" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-7194-89b6-fb7cea446469" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7285-8d0a-da6c16a5d195" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-7194-89b6-fb7cea446469" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7285-8d0a-da6c16a5d195" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7285-8d0a-da6c16a5d195_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7285-8d0a-da6c16a5d195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7285-8d0a-da6c16a5d195_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7285-8d0a-da6c16a5d195" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_A20202022VestedMYLTIPsMember_019edbbc-1fab-7858-97dd-26b7db497a96" xlink:href="bxp-20260630.xsd#bxp_A20202022VestedMYLTIPsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_bxp_A20202022VestedMYLTIPsMember_019edbbc-1fab-7858-97dd-26b7db497a96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-72e4-a91f-4835511a2a21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-72e4-a91f-4835511a2a21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPUnitsMember_019edbbc-1fab-75ad-b5a1-42b3841b02a8" xlink:href="bxp-20260630.xsd#bxp_LTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_bxp_LTIPUnitsMember_019edbbc-1fab-75ad-b5a1-42b3841b02a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPMember_019edbbc-1fab-773a-b8c8-9f10cd273a8a" xlink:href="bxp-20260630.xsd#bxp_MYLTIPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_bxp_MYLTIPMember_019edbbc-1fab-773a-b8c8-9f10cd273a8a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoZeroTwoFiveOPPMember_019edbbc-1fab-70ab-ab0f-093e3b75fb7d" xlink:href="bxp-20260630.xsd#bxp_TwoZeroTwoFiveOPPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_bxp_TwoZeroTwoFiveOPPMember_019edbbc-1fab-70ab-ab0f-093e3b75fb7d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-7656-b3ee-8a830b044b26" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7f02-8f4c-bd279a65c232" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-7656-b3ee-8a830b044b26" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock_019edbbc-1fab-701b-8fac-4dc2040b0324" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:to="loc_us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock_019edbbc-1fab-701b-8fac-4dc2040b0324" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsVestedAndExpectedToVestTableTextBlock_019edbbc-1fab-7b58-a636-edf289093d9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsVestedAndExpectedToVestTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardRestrictedStockUnitsVestedAndExpectedToVestTableTextBlock_019edbbc-1fab-7b58-a636-edf289093d9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SharedBasedCompensationArrangementByShareBasedPaymentAwardPerformanceRequirementTableTextBlock_019edbbc-1fab-7fd0-bbc1-821bcca9b853" xlink:href="bxp-20260630.xsd#bxp_SharedBasedCompensationArrangementByShareBasedPaymentAwardPerformanceRequirementTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:to="loc_bxp_SharedBasedCompensationArrangementByShareBasedPaymentAwardPerformanceRequirementTableTextBlock_019edbbc-1fab-7fd0-bbc1-821bcca9b853" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationEmployeeStockPurchasePlanActivityTableTextBlock_019edbbc-1fab-7ba7-869d-031da71bdae2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationEmployeeStockPurchasePlanActivityTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7884-80a6-b27b9173626c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationEmployeeStockPurchasePlanActivityTableTextBlock_019edbbc-1fab-7ba7-869d-031da71bdae2" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/OrganizationDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#OrganizationDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/OrganizationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1e05-7297-baee-be91bab34274" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:to="loc_srt_OwnershipAxis_019edbbc-1e05-7297-baee-be91bab34274" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1e05-7297-baee-be91bab34274_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1e05-7297-baee-be91bab34274" xlink:to="loc_srt_OwnershipDomain_019edbbc-1e05-7297-baee-be91bab34274_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1e05-7726-967c-8c9fcd787e28" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1e05-7297-baee-be91bab34274" xlink:to="loc_srt_OwnershipDomain_019edbbc-1e05-7726-967c-8c9fcd787e28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7e0c-a9ec-2255d701a3fe" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1e05-7726-967c-8c9fcd787e28" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7e0c-a9ec-2255d701a3fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1e05-7918-a4f4-e3edba782bec" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1e05-7918-a4f4-e3edba782bec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-7918-a4f4-e3edba782bec_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1e05-7918-a4f4-e3edba782bec" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-7918-a4f4-e3edba782bec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1e05-7918-a4f4-e3edba782bec" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-783f-b6b3-85020dc90242" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:to="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-783f-b6b3-85020dc90242" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OfficeBuildingMember_019edbbc-1e05-7a01-801b-b9eba68b69c5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OfficeBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:to="loc_srt_OfficeBuildingMember_019edbbc-1e05-7a01-801b-b9eba68b69c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RetailSiteMember_019edbbc-1e05-7cc6-b2df-f2b262aa4cdd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RetailSiteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:to="loc_srt_RetailSiteMember_019edbbc-1e05-7cc6-b2df-f2b262aa4cdd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ApartmentBuildingMember_019edbbc-1e05-710c-9115-7040c3f0b6d3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ApartmentBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:to="loc_srt_ApartmentBuildingMember_019edbbc-1e05-710c-9115-7040c3f0b6d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_HotelMember_019edbbc-1e05-7ad9-b235-fda9aa216565" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_HotelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1e05-75df-9f4f-e46fb5e90ea9" xlink:to="loc_srt_HotelMember_019edbbc-1e05-7ad9-b235-fda9aa216565" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1e05-7954-adfb-c13a846522ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1e05-7954-adfb-c13a846522ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1e05-7954-adfb-c13a846522ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1e05-7954-adfb-c13a846522ae" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1e05-7954-adfb-c13a846522ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1e05-7f05-861d-7c437ffbc432" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1e05-7954-adfb-c13a846522ae" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1e05-7f05-861d-7c437ffbc432" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019edbbc-1e05-7bf8-a305-51f95b9aba9a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1e05-7f05-861d-7c437ffbc432" xlink:to="loc_us-gaap_ConstructionInProgressMember_019edbbc-1e05-7bf8-a305-51f95b9aba9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7e4c-a287-f315c7ba7eaf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7e4c-a287-f315c7ba7eaf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7e4c-a287-f315c7ba7eaf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7e4c-a287-f315c7ba7eaf" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7e4c-a287-f315c7ba7eaf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7583-95eb-2c10762239e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7e4c-a287-f315c7ba7eaf" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7583-95eb-2c10762239e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-7eb3-8cb7-d7f3bcca0b1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7583-95eb-2c10762239e8" xlink:to="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-7eb3-8cb7-d7f3bcca0b1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-714f-a84b-6c7064f7f8d3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1e05-75fd-9cff-1f1454271a45" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-714f-a84b-6c7064f7f8d3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-714f-a84b-6c7064f7f8d3_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-714f-a84b-6c7064f7f8d3" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-714f-a84b-6c7064f7f8d3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7cf4-88c3-f183edfedb63" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-714f-a84b-6c7064f7f8d3" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7cf4-88c3-f183edfedb63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1e05-70cf-8e66-ff4abd8258a5" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7cf4-88c3-f183edfedb63" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1e05-70cf-8e66-ff4abd8258a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest_019edbbc-1e05-7031-b3bb-2cce19f937b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest_019edbbc-1e05-7031-b3bb-2cce19f937b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RestrictionOnRedemptionOfOpUnitsFromDateOfIssuanceInYears_019edbbc-1e05-764a-ac06-1a24dbf331b2" xlink:href="bxp-20260630.xsd#bxp_RestrictionOnRedemptionOfOpUnitsFromDateOfIssuanceInYears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_bxp_RestrictionOnRedemptionOfOpUnitsFromDateOfIssuanceInYears_019edbbc-1e05-764a-ac06-1a24dbf331b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CommonStockConversionRate_019edbbc-1e05-7d87-861c-7aa8bc573871" xlink:href="bxp-20260630.xsd#bxp_CommonStockConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_bxp_CommonStockConversionRate_019edbbc-1e05-7d87-861c-7aa8bc573871" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitConversionRate_019edbbc-1e05-7c0d-87c6-8a894520c2ce" xlink:href="bxp-20260630.xsd#bxp_OpUnitConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_bxp_OpUnitConversionRate_019edbbc-1e05-7c0d-87c6-8a894520c2ce" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPUnitConversionRate_019edbbc-1e05-741d-b383-3c4400a87174" xlink:href="bxp-20260630.xsd#bxp_LTIPUnitConversionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_bxp_LTIPUnitConversionRate_019edbbc-1e05-741d-b383-3c4400a87174" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019edbbc-1e05-795e-96a6-a30e0ebf0f45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019edbbc-1e05-795e-96a6-a30e0ebf0f45" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_019edbbc-1e05-7e16-9769-91f601550465" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_019edbbc-1e05-7e16-9769-91f601550465" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1e05-7b15-9178-2cf1dbc82613" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1e05-7b15-9178-2cf1dbc82613" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NumberOfVIEs_019edbbc-1e05-7656-a918-96a75b01ecbd" xlink:href="bxp-20260630.xsd#bxp_NumberOfVIEs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1e05-7286-86f1-bae978f22fc0" xlink:to="loc_bxp_NumberOfVIEs_019edbbc-1e05-7656-a918-96a75b01ecbd" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SummaryOfSignificantAccountingPoliciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:href="bxp-20260630.xsd#bxp_SummaryOfSignificantAccountingPoliciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7a69-b4cf-5acd06867178" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7a69-b4cf-5acd06867178" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7a69-b4cf-5acd06867178_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7a69-b4cf-5acd06867178" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7a69-b4cf-5acd06867178_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1e05-7a69-b4cf-5acd06867178" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TotalOfficePropertiesMember_019edbbc-1e05-7d84-be3c-65f223bcd41e" xlink:href="bxp-20260630.xsd#bxp_TotalOfficePropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:to="loc_bxp_TotalOfficePropertiesMember_019edbbc-1e05-7d84-be3c-65f223bcd41e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1e05-7785-8c24-5ebca3bcb4fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1e05-7785-8c24-5ebca3bcb4fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-70df-8798-538fced0fb1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialRealEstateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:to="loc_us-gaap_CommercialRealEstateMember_019edbbc-1e05-70df-8798-538fced0fb1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WhollyOwnedPropertiesMember_019edbbc-1e05-7b0d-9620-915429b6c82c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WhollyOwnedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1e05-7828-a941-9a4a58145537" xlink:to="loc_us-gaap_WhollyOwnedPropertiesMember_019edbbc-1e05-7b0d-9620-915429b6c82c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7b24-b2ab-4d56b5c301db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7b24-b2ab-4d56b5c301db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7b24-b2ab-4d56b5c301db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7b24-b2ab-4d56b5c301db" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7b24-b2ab-4d56b5c301db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7ad1-a496-b1a360df246b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1e05-7b24-b2ab-4d56b5c301db" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7ad1-a496-b1a360df246b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019edbbc-1e05-7bc9-8052-5c541caca400" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7ad1-a496-b1a360df246b" xlink:to="loc_us-gaap_RetainedEarningsMember_019edbbc-1e05-7bc9-8052-5c541caca400" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1e05-7880-b267-fb332ffe3f02" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7ad1-a496-b1a360df246b" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019edbbc-1e05-7880-b267-fb332ffe3f02" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-7281-8c8d-98c940e1fb6e" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestpropertypartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1e05-7ad1-a496-b1a360df246b" xlink:to="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1e05-7281-8c8d-98c940e1fb6e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1e05-730a-af4d-68e97922cedd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1e05-730a-af4d-68e97922cedd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-730a-af4d-68e97922cedd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1e05-730a-af4d-68e97922cedd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-730a-af4d-68e97922cedd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-7242-b288-d157e3f37842" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1e05-730a-af4d-68e97922cedd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-7242-b288-d157e3f37842" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesMember_019edbbc-1e05-7df8-b4c9-cf873aef95bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-7242-b288-d157e3f37842" xlink:to="loc_us-gaap_MortgagesMember_019edbbc-1e05-7df8-b4c9-cf873aef95bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019edbbc-1e05-7ada-99a5-3c27730674ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-7242-b288-d157e3f37842" xlink:to="loc_us-gaap_LineOfCreditMember_019edbbc-1e05-7ada-99a5-3c27730674ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebtMember_019edbbc-1e05-767f-9b04-ab7ab864caa5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1e05-7242-b288-d157e3f37842" xlink:to="loc_us-gaap_ConvertibleDebtMember_019edbbc-1e05-767f-9b04-ab7ab864caa5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-73b8-8003-f9483dbf9fa7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-73b8-8003-f9483dbf9fa7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-73b8-8003-f9483dbf9fa7_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-73b8-8003-f9483dbf9fa7" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-73b8-8003-f9483dbf9fa7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7d89-80b4-f51d4581b421" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019edbbc-1e05-73b8-8003-f9483dbf9fa7" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7d89-80b4-f51d4581b421" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SubsidiariesMember_019edbbc-1e05-76ca-b499-b12d682b2c39" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7d89-80b4-f51d4581b421" xlink:to="loc_srt_SubsidiariesMember_019edbbc-1e05-76ca-b499-b12d682b2c39" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019edbbc-1e05-78e0-939c-60861a3a4ea3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7d89-80b4-f51d4581b421" xlink:to="loc_srt_ParentCompanyMember_019edbbc-1e05-78e0-939c-60861a3a4ea3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019edbbc-1e05-7005-ab87-5175bd9a9f7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019edbbc-1e05-7d89-80b4-f51d4581b421" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019edbbc-1e05-7005-ab87-5175bd9a9f7b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_019edbbc-1e05-79c9-9856-d235fbb3816c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_019edbbc-1e05-79c9-9856-d235fbb3816c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_019edbbc-1e05-79c9-9856-d235fbb3816c_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_019edbbc-1e05-79c9-9856-d235fbb3816c" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_019edbbc-1e05-79c9-9856-d235fbb3816c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_019edbbc-1e05-789f-8659-a7d4a70b8ba6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionAxis_019edbbc-1e05-79c9-9856-d235fbb3816c" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_019edbbc-1e05-789f-8659-a7d4a70b8ba6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_019edbbc-1e05-7aa5-9cee-1c9ec2e61269" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CumulativeEffectPeriodOfAdoptionDomain_019edbbc-1e05-789f-8659-a7d4a70b8ba6" xlink:to="loc_srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_019edbbc-1e05-7aa5-9cee-1c9ec2e61269" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019edbbc-1e05-7755-a2f4-0db9c4f994c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_InvestmentTypeAxis_019edbbc-1e05-7755-a2f4-0db9c4f994c2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1e05-7755-a2f4-0db9c4f994c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019edbbc-1e05-7755-a2f4-0db9c4f994c2" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1e05-7755-a2f4-0db9c4f994c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1e05-7c6f-a8c5-6df9d6f44723" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019edbbc-1e05-7755-a2f4-0db9c4f994c2" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1e05-7c6f-a8c5-6df9d6f44723" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EnvironmentalFocusedInvestmentFundMember_019edbbc-1e05-7f2a-a525-dc4dca0f463d" xlink:href="bxp-20260630.xsd#bxp_EnvironmentalFocusedInvestmentFundMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1e05-7c6f-a8c5-6df9d6f44723" xlink:to="loc_bxp_EnvironmentalFocusedInvestmentFundMember_019edbbc-1e05-7f2a-a525-dc4dca0f463d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7d83-800e-ddbd3b955df3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7d83-800e-ddbd3b955df3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7d83-800e-ddbd3b955df3_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7d83-800e-ddbd3b955df3" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-7d83-800e-ddbd3b955df3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-752a-b20e-89edd5818e55" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1e05-7d83-800e-ddbd3b955df3" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-752a-b20e-89edd5818e55" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_DockSevenTwoMember_019edbbc-1e05-7138-a528-947aab10a615" xlink:href="bxp-20260630.xsd#bxp_DockSevenTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-752a-b20e-89edd5818e55" xlink:to="loc_bxp_DockSevenTwoMember_019edbbc-1e05-7138-a528-947aab10a615" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ShadyGroveInnovationDistrictMember_019edbbc-1e05-7830-aca2-d9aa33043e17" xlink:href="bxp-20260630.xsd#bxp_ShadyGroveInnovationDistrictMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-752a-b20e-89edd5818e55" xlink:to="loc_bxp_ShadyGroveInnovationDistrictMember_019edbbc-1e05-7830-aca2-d9aa33043e17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumnerSquareMember_019fb50d-f73c-75fc-9612-35f2e12b81fd" xlink:href="bxp-20260630.xsd#bxp_SumnerSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1e05-752a-b20e-89edd5818e55" xlink:to="loc_bxp_SumnerSquareMember_019fb50d-f73c-75fc-9612-35f2e12b81fd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_019edbbc-1e05-7788-bf8f-d299163477e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_019edbbc-1e05-7788-bf8f-d299163477e8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7788-bf8f-d299163477e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_019edbbc-1e05-7788-bf8f-d299163477e8" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7788-bf8f-d299163477e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7906-a4ca-8e826f908d15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedByTypeAxis_019edbbc-1e05-7788-bf8f-d299163477e8" xlink:to="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7906-a4ca-8e826f908d15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsComplexMember_019edbbc-1e05-7cd4-91d1-e6fa214251cc" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsComplexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7906-a4ca-8e826f908d15" xlink:to="loc_bxp_GatewayCommonsComplexMember_019edbbc-1e05-7cd4-91d1-e6fa214251cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ColoradoCenterGatewayCommonsAndSafecoPlazaMember_019edbbc-1e05-7457-aa73-18e34e760cb2" xlink:href="bxp-20260630.xsd#bxp_ColoradoCenterGatewayCommonsAndSafecoPlazaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7906-a4ca-8e826f908d15" xlink:to="loc_bxp_ColoradoCenterGatewayCommonsAndSafecoPlazaMember_019edbbc-1e05-7457-aa73-18e34e760cb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PlatformSixteenThreeSixZeroParkAvenueSouthTwoZeroZeroFifthAvenueAndSafecoPlazaMember_019edbbc-1e05-76ac-b8b7-fd314e57e7dc" xlink:href="bxp-20260630.xsd#bxp_PlatformSixteenThreeSixZeroParkAvenueSouthTwoZeroZeroFifthAvenueAndSafecoPlazaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairedLongLivedAssetsHeldAndUsedAssetNameDomain_019edbbc-1e05-7906-a4ca-8e826f908d15" xlink:to="loc_bxp_PlatformSixteenThreeSixZeroParkAvenueSouthTwoZeroZeroFifthAvenueAndSafecoPlazaMember_019edbbc-1e05-76ac-b8b7-fd314e57e7dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_019edbbc-1e05-731f-b863-14d72cfbc11b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_019edbbc-1e05-731f-b863-14d72cfbc11b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_019edbbc-1e05-731f-b863-14d72cfbc11b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_019edbbc-1e05-731f-b863-14d72cfbc11b" xlink:to="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_019edbbc-1e05-731f-b863-14d72cfbc11b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_019edbbc-1e05-78c4-98f8-d33daf0c6bca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DeferredCompensationArrangementWithIndividualExcludingShareBasedPaymentsAndPostretirementBenefitsByTypeOfDeferredCompensationAxis_019edbbc-1e05-731f-b863-14d72cfbc11b" xlink:to="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_019edbbc-1e05-78c4-98f8-d33daf0c6bca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCompensationExcludingShareBasedPaymentsAndRetirementBenefitsMember_019edbbc-1e05-7ea1-9fb9-d88287105c4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCompensationExcludingShareBasedPaymentsAndRetirementBenefitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredBonusAndProfitSharingArrangementIndividualContractTypeOfDeferredCompensationDomain_019edbbc-1e05-78c4-98f8-d33daf0c6bca" xlink:to="loc_us-gaap_DeferredCompensationExcludingShareBasedPaymentsAndRetirementBenefitsMember_019edbbc-1e05-7ea1-9fb9-d88287105c4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1e05-76eb-be3a-f389d5295388" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1e05-76eb-be3a-f389d5295388" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-76eb-be3a-f389d5295388_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-76eb-be3a-f389d5295388" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-76eb-be3a-f389d5295388_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1e05-7afe-9c0f-c0fe0b90345b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1e05-76eb-be3a-f389d5295388" xlink:to="loc_dei_EntityDomain_019edbbc-1e05-7afe-9c0f-c0fe0b90345b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1e05-78fa-8e43-7313ab20062c" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7afe-9c0f-c0fe0b90345b" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1e05-78fa-8e43-7313ab20062c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7770-9655-3f6233b3d956" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1e05-7afe-9c0f-c0fe0b90345b" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1e05-7770-9655-3f6233b3d956" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-73dd-a67c-1f510a81f5c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-73dd-a67c-1f510a81f5c1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-73dd-a67c-1f510a81f5c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-73dd-a67c-1f510a81f5c1" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-73dd-a67c-1f510a81f5c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7521-a419-47d498231253" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_019edbbc-1e05-73dd-a67c-1f510a81f5c1" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7521-a419-47d498231253" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_019edbbc-1e05-7fc1-993b-52e3f91f93f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_019edbbc-1e05-7521-a419-47d498231253" xlink:to="loc_us-gaap_CommercialPaperMember_019edbbc-1e05-7fc1-993b-52e3f91f93f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1e05-74f9-b79b-c811a8e00a3e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1e05-74f9-b79b-c811a8e00a3e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1e05-74f9-b79b-c811a8e00a3e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1e05-74f9-b79b-c811a8e00a3e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1e05-74f9-b79b-c811a8e00a3e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1e05-7038-8d60-cc6c10f62199" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1e05-74f9-b79b-c811a8e00a3e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1e05-7038-8d60-cc6c10f62199" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCapMember_019edbbc-1e05-79fe-8b5f-ebd0e585414a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateCapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1e05-7038-8d60-cc6c10f62199" xlink:to="loc_us-gaap_InterestRateCapMember_019edbbc-1e05-79fe-8b5f-ebd0e585414a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_019edbbc-1e05-7897-a4f0-97f5e009803d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_019edbbc-1e05-7897-a4f0-97f5e009803d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_019edbbc-1e05-7897-a4f0-97f5e009803d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_019edbbc-1e05-7897-a4f0-97f5e009803d" xlink:to="loc_us-gaap_TypeOfAdoptionMember_019edbbc-1e05-7897-a4f0-97f5e009803d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfAdoptionMember_019edbbc-1e05-7295-a3ae-27cd7b3cd77b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfAdoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_019edbbc-1e05-7897-a4f0-97f5e009803d" xlink:to="loc_us-gaap_TypeOfAdoptionMember_019edbbc-1e05-7295-a3ae-27cd7b3cd77b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountingStandardsUpdate202305Member_019edbbc-1e05-7fd9-a4b3-6ad5a263eba2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountingStandardsUpdate202305Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_019edbbc-1e05-7295-a3ae-27cd7b3cd77b" xlink:to="loc_us-gaap_AccountingStandardsUpdate202305Member_019edbbc-1e05-7fd9-a4b3-6ad5a263eba2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019edbbc-1e05-7c55-8e48-3a0371220a72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1e05-7e3f-bef3-77f50d7ea4eb" xlink:to="loc_us-gaap_DebtInstrumentAxis_019edbbc-1e05-7c55-8e48-3a0371220a72" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1e05-7c55-8e48-3a0371220a72_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1e05-7c55-8e48-3a0371220a72" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1e05-7c55-8e48-3a0371220a72_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1e05-7492-8665-d64f0e2ef88a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1e05-7c55-8e48-3a0371220a72" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1e05-7492-8665-d64f0e2ef88a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoPointZeroZeroPercentUnsecuredExchangeableSeniorNotesMember_019edbbc-1e05-7708-a9d2-7a1d59373adb" xlink:href="bxp-20260630.xsd#bxp_TwoPointZeroZeroPercentUnsecuredExchangeableSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1e05-7492-8665-d64f0e2ef88a" xlink:to="loc_bxp_TwoPointZeroZeroPercentUnsecuredExchangeableSeniorNotesMember_019edbbc-1e05-7708-a9d2-7a1d59373adb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SalariesAndRelatedCostsCapitalized_019edbbc-1e05-7aab-8b82-173a653e33fc" xlink:href="bxp-20260630.xsd#bxp_SalariesAndRelatedCostsCapitalized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_SalariesAndRelatedCostsCapitalized_019edbbc-1e05-7aab-8b82-173a653e33fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CashFDICInsuredLimit_019edbbc-1e05-775e-9212-ae9cc0da5cf6" xlink:href="bxp-20260630.xsd#bxp_CashFDICInsuredLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_CashFDICInsuredLimit_019edbbc-1e05-775e-9212-ae9cc0da5cf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SeparateUnrestrictedCashForDeferredCompensationPlan_019edbbc-1e05-7e08-b7db-a2b69c0b1fdd" xlink:href="bxp-20260630.xsd#bxp_SeparateUnrestrictedCashForDeferredCompensationPlan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_SeparateUnrestrictedCashForDeferredCompensationPlan_019edbbc-1e05-7e08-b7db-a2b69c0b1fdd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_019edbbc-1e05-7b05-97a9-eb8eec75bd76" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_GainLossOnInvestments_019edbbc-1e05-7b05-97a9-eb8eec75bd76" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_U.S.TreasuryBillTermOfContract_019edbbc-1e05-7e2b-91e5-ae6ba1be40d7" xlink:href="bxp-20260630.xsd#bxp_U.S.TreasuryBillTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_U.S.TreasuryBillTermOfContract_019edbbc-1e05-7e2b-91e5-ae6ba1be40d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USGovernmentSecuritiesAtCarryingValue_019edbbc-1e05-7623-ad46-765f3753cc58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USGovernmentSecuritiesAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_USGovernmentSecuritiesAtCarryingValue_019edbbc-1e05-7623-ad46-765f3753cc58" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-72e3-81f5-6733501c43ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_019edbbc-1e05-72e3-81f5-6733501c43ca" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019edbbc-1e05-73af-a8b8-abde5d591539" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019edbbc-1e05-73af-a8b8-abde5d591539" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AccountsReceivableCollectionPeriodExpected_019edbbc-1e05-7e47-826f-3cdeaa8adf83" xlink:href="bxp-20260630.xsd#bxp_AccountsReceivableCollectionPeriodExpected"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_AccountsReceivableCollectionPeriodExpected_019edbbc-1e05-7e47-826f-3cdeaa8adf83" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1e05-7683-84c2-77d91e903d0c" xlink:href="bxp-20260630.xsd#bxp_AboveAndBelowMarketRentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1e05-7683-84c2-77d91e903d0c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaper_019edbbc-1e05-76ed-896f-8674170df758" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_CommercialPaper_019edbbc-1e05-76ed-896f-8674170df758" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_019edbbc-1e05-7e3a-a436-563a756bb6aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_DerivativeNumberOfInstrumentsHeld_019edbbc-1e05-7e3a-a436-563a756bb6aa" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019edbbc-1e05-7afc-8397-d9e203e60e2d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019edbbc-1e05-7afc-8397-d9e203e60e2d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_019edbbc-1e05-70b6-ad6a-93f42d6318cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_GainLossOnFairValueHedgesRecognizedInEarnings_019edbbc-1e05-70b6-ad6a-93f42d6318cf" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashEquivalentsAtCarryingValue_019edbbc-1e05-7bad-b719-4c81f1d82034" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_CashEquivalentsAtCarryingValue_019edbbc-1e05-7bad-b719-4c81f1d82034" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_REITDistributionRequirement_019edbbc-1e05-7747-a544-bb9efa208062" xlink:href="bxp-20260630.xsd#bxp_REITDistributionRequirement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_REITDistributionRequirement_019edbbc-1e05-7747-a544-bb9efa208062" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysTaxableIncomeDistribution_019edbbc-1e05-792a-8713-a8f75b2e84e5" xlink:href="bxp-20260630.xsd#bxp_CompanysTaxableIncomeDistribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_CompanysTaxableIncomeDistribution_019edbbc-1e05-792a-8713-a8f75b2e84e5" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherInvestments_019edbbc-1e05-7f1b-8c0b-4b5f5b34a704" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_OtherInvestments_019edbbc-1e05-7f1b-8c0b-4b5f5b34a704" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_019edbbc-1e05-7999-a6cf-55d5eca1af84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_019edbbc-1e05-7999-a6cf-55d5eca1af84" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_019edbbc-1e05-717a-a34e-c34b446ff4a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_019edbbc-1e05-717a-a34e-c34b446ff4a9" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NumberOfVIEs_019edbbc-1e05-7245-a4ea-6bc3b59c0bb9" xlink:href="bxp-20260630.xsd#bxp_NumberOfVIEs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_bxp_NumberOfVIEs_019edbbc-1e05-7245-a4ea-6bc3b59c0bb9" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1e05-7a7e-8d7d-26cad98e4dd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1e05-7a7e-8d7d-26cad98e4dd8" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1e05-70ec-9d78-b02c616105e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1e05-70ec-9d78-b02c616105e0" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019edbbc-1e05-7a1f-a7c4-2aa9c3f0f0d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_SummaryOfSignificantAccountingPoliciesLineItems_019edbbc-1e05-727e-adca-7164b0b997c1" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019edbbc-1e05-7a1f-a7c4-2aa9c3f0f0d9" xlink:type="arc" order="23"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesCarryingValueOfIndebtednessAndCorrespondingEstimateOfFairValueDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SummaryOfSignificantAccountingPoliciesCarryingValueOfIndebtednessAndCorrespondingEstimateOfFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesCarryingValueOfIndebtednessAndCorrespondingEstimateOfFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019edbbc-1ec9-7861-b048-0d91372bbce0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019edbbc-1ec9-7861-b048-0d91372bbce0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019edbbc-1ec9-7147-b36e-364420aec313" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019edbbc-1ec9-7861-b048-0d91372bbce0" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019edbbc-1ec9-7147-b36e-364420aec313" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019edbbc-1ec9-7147-b36e-364420aec313_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019edbbc-1ec9-7147-b36e-364420aec313" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019edbbc-1ec9-7147-b36e-364420aec313_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019edbbc-1ec9-7021-b527-7065e536ef34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019edbbc-1ec9-7147-b36e-364420aec313" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019edbbc-1ec9-7021-b527-7065e536ef34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019fc85b-73c0-75c4-be78-c3af0db3cef6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019edbbc-1ec9-7021-b527-7065e536ef34" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019fc85b-73c0-75c4-be78-c3af0db3cef6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019edbbc-1ec9-7e24-8bc2-2037e5dc93d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019fc85b-73c0-75c4-be78-c3af0db3cef6" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019edbbc-1ec9-7e24-8bc2-2037e5dc93d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019edbbc-1ec9-7b48-91f9-46c88f2965b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019fc85b-73c0-75c4-be78-c3af0db3cef6" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019edbbc-1ec9-7b48-91f9-46c88f2965b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1ec9-7711-a9d5-8de5969f1bff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019edbbc-1ec9-7861-b048-0d91372bbce0" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1ec9-7711-a9d5-8de5969f1bff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7711-a9d5-8de5969f1bff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1ec9-7711-a9d5-8de5969f1bff" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7711-a9d5-8de5969f1bff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7c92-b555-d67a3928a6c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1ec9-7711-a9d5-8de5969f1bff" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7c92-b555-d67a3928a6c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019edbbc-1ec9-7f01-ae25-82c7f3b20db8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7c92-b555-d67a3928a6c4" xlink:to="loc_us-gaap_RelatedPartyMember_019edbbc-1ec9-7f01-ae25-82c7f3b20db8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019edbbc-1ec9-7ecd-9119-3762580881c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019edbbc-1ec9-7c92-b555-d67a3928a6c4" xlink:to="loc_us-gaap_NonrelatedPartyMember_019edbbc-1ec9-7ecd-9119-3762580881c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019edbbc-1ec9-70df-baa2-b0ed49d195cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019edbbc-1ec9-7861-b048-0d91372bbce0" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019edbbc-1ec9-70df-baa2-b0ed49d195cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-70df-baa2-b0ed49d195cb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019edbbc-1ec9-70df-baa2-b0ed49d195cb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-70df-baa2-b0ed49d195cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-7e8f-84de-b28b19b9e3e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019edbbc-1ec9-70df-baa2-b0ed49d195cb" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-7e8f-84de-b28b19b9e3e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019edbbc-1ec9-7bc0-9348-5bc0b66d222d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-7e8f-84de-b28b19b9e3e3" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019edbbc-1ec9-7bc0-9348-5bc0b66d222d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019edbbc-1ec9-711a-8c82-1979b59c5649" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019edbbc-1ec9-7e8f-84de-b28b19b9e3e3" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019edbbc-1ec9-711a-8c82-1979b59c5649" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_019edbbc-1ec9-74f3-a300-d70c756111a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_NotesReceivableNet_019edbbc-1ec9-74f3-a300-d70c756111a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_019edbbc-1ec9-7863-808c-53e35151ae31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_NotesReceivableGross_019edbbc-1ec9-7863-808c-53e35151ae31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent_019edbbc-1ec9-7658-93fa-bc68c47d33fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_SalesTypeLeaseNetInvestmentInLeaseAfterAllowanceForCreditLossCurrent_019edbbc-1ec9-7658-93fa-bc68c47d33fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019edbbc-1ec9-739b-89c0-7ade45225639" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019edbbc-1ec9-739b-89c0-7ade45225639" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019edbbc-1ec9-7572-89ae-a76ad052848b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_SeniorNotes_019edbbc-1ec9-7572-89ae-a76ad052848b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertibleDebt_019edbbc-1ec9-7843-b66c-e2d753e554f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConvertibleDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_ConvertibleDebt_019edbbc-1ec9-7843-b66c-e2d753e554f1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaper_019edbbc-1ec9-72c1-abc4-114270cc6700" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_CommercialPaper_019edbbc-1ec9-72c1-abc4-114270cc6700" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_019edbbc-1ec9-7935-af6a-df6963b2741f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_DebtInstrumentFairValue_019edbbc-1ec9-7935-af6a-df6963b2741f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_019edbbc-1ec9-7ed3-8c35-49a4ed4fc370" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_SecuredDebt_019edbbc-1ec9-7ed3-8c35-49a4ed4fc370" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019edbbc-1ec9-7429-8036-e42c1e22b90d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_LineOfCredit_019edbbc-1ec9-7429-8036-e42c1e22b90d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherBorrowings_019edbbc-1ec9-7ca9-aa33-97278eb9c1c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_OtherBorrowings_019edbbc-1ec9-7ca9-aa33-97278eb9c1c6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019edbbc-1ec9-7329-a1e7-8b319eccdb4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019edbbc-1ec9-7bc1-a8f6-bf25b5ceb434" xlink:to="loc_us-gaap_LongTermDebt_019edbbc-1ec9-7329-a1e7-8b319eccdb4f" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesFairValueofDerivativesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SummaryOfSignificantAccountingPoliciesFairValueofDerivativesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SummaryOfSignificantAccountingPoliciesFairValueofDerivativesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_019edbbc-1ec9-767c-af5f-0b27372b1bfc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019edbbc-1ec9-772a-89c2-311799f1bbc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019edbbc-1ec9-767c-af5f-0b27372b1bfc" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019edbbc-1ec9-772a-89c2-311799f1bbc3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1ec9-70c2-bb6a-50370363f8e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_019edbbc-1ec9-772a-89c2-311799f1bbc3" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1ec9-70c2-bb6a-50370363f8e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1ec9-70c2-bb6a-50370363f8e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1ec9-70c2-bb6a-50370363f8e4" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1ec9-70c2-bb6a-50370363f8e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1ec9-7d36-b275-bd8b5ff3f9dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1ec9-70c2-bb6a-50370363f8e4" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1ec9-7d36-b275-bd8b5ff3f9dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019edbbc-1ec9-7b50-8b91-4b4c4d819fbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1ec9-7d36-b275-bd8b5ff3f9dd" xlink:to="loc_us-gaap_InterestRateSwapMember_019edbbc-1ec9-7b50-8b91-4b4c4d819fbd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgeDerivativeInstrumentLiabilitiesAtFairValue_019edbbc-1ec9-70e5-84f7-719f35802085" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashFlowHedgeDerivativeInstrumentLiabilitiesAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019edbbc-1ec9-767c-af5f-0b27372b1bfc" xlink:to="loc_us-gaap_CashFlowHedgeDerivativeInstrumentLiabilitiesAtFairValue_019edbbc-1ec9-70e5-84f7-719f35802085" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue_019fb4f6-857a-7039-9aa1-d4804c6a9077" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_019edbbc-1ec9-767c-af5f-0b27372b1bfc" xlink:to="loc_us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue_019fb4f6-857a-7039-9aa1-d4804c6a9077" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/RealEstateScheduleofRealEstatePropertiesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#RealEstateScheduleofRealEstatePropertiesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/RealEstateScheduleofRealEstatePropertiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7640-a8a2-fe1e54b3ea8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7640-a8a2-fe1e54b3ea8e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-70b6-bfa4-319e98d04812" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7640-a8a2-fe1e54b3ea8e" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-70b6-bfa4-319e98d04812" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-70b6-bfa4-319e98d04812_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-70b6-bfa4-319e98d04812" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-70b6-bfa4-319e98d04812_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7b35-adff-67cabb17a711" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-70b6-bfa4-319e98d04812" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7b35-adff-67cabb17a711" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7fde-a7ed-4ae9e0b2d711" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-7b35-adff-67cabb17a711" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7fde-a7ed-4ae9e0b2d711" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Land_019edbbc-1ec9-7894-b0c3-74bba54c9779" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Land"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_Land_019edbbc-1ec9-7894-b0c3-74bba54c9779" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseRightOfUseAsset_019edbbc-1ec9-7b36-9401-f8d1e379a143" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinanceLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_FinanceLeaseRightOfUseAsset_019edbbc-1ec9-7b36-9401-f8d1e379a143" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1ec9-7eed-b0d2-587eaee72c01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1ec9-7eed-b0d2-587eaee72c01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandAvailableForDevelopment_019edbbc-1ec9-7204-8e25-5f50def3adb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandAvailableForDevelopment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_LandAvailableForDevelopment_019edbbc-1ec9-7204-8e25-5f50def3adb6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentBuildingAndBuildingImprovements_019edbbc-1ec9-7daa-a0d3-685ee6840a83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentBuildingAndBuildingImprovements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_InvestmentBuildingAndBuildingImprovements_019edbbc-1ec9-7daa-a0d3-685ee6840a83" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseholdImprovementsGross_019edbbc-1ec9-7596-8652-90cff17c98e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LeaseholdImprovementsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_LeaseholdImprovementsGross_019edbbc-1ec9-7596-8652-90cff17c98e3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesGross_019edbbc-1ec9-7f85-a0fd-00420e812531" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FurnitureAndFixturesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_FurnitureAndFixturesGross_019edbbc-1ec9-7f85-a0fd-00420e812531" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressGross_019edbbc-1ec9-7b2b-ab6e-cfdbe3895763" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionInProgressGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_ConstructionInProgressGross_019edbbc-1ec9-7b2b-ab6e-cfdbe3895763" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RealEstateInvestmentPropertyAtCostIncludingRightofUseAssets_019edbbc-1ec9-708b-82c8-7e50adbf2ff7" xlink:href="bxp-20260630.xsd#bxp_RealEstateInvestmentPropertyAtCostIncludingRightofUseAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_bxp_RealEstateInvestmentPropertyAtCostIncludingRightofUseAssets_019edbbc-1ec9-708b-82c8-7e50adbf2ff7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1ec9-7514-9ec0-86c7692bd1d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019edbbc-1ec9-7514-9ec0-86c7692bd1d2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1ec9-7227-9caf-b72057b2767a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7120-b382-2f652c10b0df" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1ec9-7227-9caf-b72057b2767a" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/RealEstateScheduleofAssetsHeldforSaleDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#RealEstateScheduleofAssetsHeldforSaleDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/RealEstateScheduleofAssetsHeldforSaleDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongLivedAssetsHeldForSaleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019fb536-f4be-74ce-bc6b-a5d723464cef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019fb536-f4be-74ce-bc6b-a5d723464cef" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis_019fb53d-6f58-7f9a-b975-a472a354dd9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019fb536-f4be-74ce-bc6b-a5d723464cef" xlink:to="loc_us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis_019fb53d-6f58-7f9a-b975-a472a354dd9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleNameDomain_019fb53d-6f58-7f9a-b975-a472a354dd9f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongLivedAssetsHeldForSaleNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis_019fb53d-6f58-7f9a-b975-a472a354dd9f" xlink:to="loc_us-gaap_LongLivedAssetsHeldForSaleNameDomain_019fb53d-6f58-7f9a-b975-a472a354dd9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongLivedAssetsHeldForSaleNameDomain_019fb53d-6f58-7e9c-942d-b10cb7b4723b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongLivedAssetsHeldForSaleNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis_019fb53d-6f58-7f9a-b975-a472a354dd9f" xlink:to="loc_us-gaap_LongLivedAssetsHeldForSaleNameDomain_019fb53d-6f58-7e9c-942d-b10cb7b4723b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumnerSquareMember_019fb536-f4be-7781-b5cf-6e7a8fefdf2f" xlink:href="bxp-20260630.xsd#bxp_SumnerSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleNameDomain_019fb53d-6f58-7e9c-942d-b10cb7b4723b" xlink:to="loc_bxp_SumnerSquareMember_019fb536-f4be-7781-b5cf-6e7a8fefdf2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019fb883-b809-7f17-ba09-f5650b48f44f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019fb536-f4be-74ce-bc6b-a5d723464cef" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019fb883-b809-7f17-ba09-f5650b48f44f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019fb883-b809-7f17-ba09-f5650b48f44f_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019fb883-b809-7f17-ba09-f5650b48f44f" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019fb883-b809-7f17-ba09-f5650b48f44f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019fb883-b809-709a-8790-a3ea68a9238f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019fb883-b809-7f17-ba09-f5650b48f44f" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019fb883-b809-709a-8790-a3ea68a9238f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumnerSquareMember_019fb883-b809-76bd-b9de-795c1c304751" xlink:href="bxp-20260630.xsd#bxp_SumnerSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019fb883-b809-709a-8790-a3ea68a9238f" xlink:to="loc_bxp_SumnerSquareMember_019fb883-b809-76bd-b9de-795c1c304751" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019fb912-a4ac-7098-8d1a-73a17598e65f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfLongLivedAssetsHeldForSaleTable_019fb536-f4be-74ce-bc6b-a5d723464cef" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019fb912-a4ac-7098-8d1a-73a17598e65f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019fb912-a4ac-7098-8d1a-73a17598e65f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019fb912-a4ac-7098-8d1a-73a17598e65f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019fb912-a4ac-7098-8d1a-73a17598e65f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019fb912-a4ac-7459-b330-817462be8ee0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019fb912-a4ac-7098-8d1a-73a17598e65f" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019fb912-a4ac-7459-b330-817462be8ee0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_019fb913-1dcb-7812-b4c0-33baa0ded8d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019fb912-a4ac-7459-b330-817462be8ee0" xlink:to="loc_us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember_019fb913-1dcb-7812-b4c0-33baa0ded8d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019fb536-f4be-7d57-952c-58b4afaeaeae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019fb536-f4be-7d57-952c-58b4afaeaeae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019fb536-f4be-7d35-8020-ebd1777e5e4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019fb536-f4be-7d35-8020-ebd1777e5e4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019fb536-f4be-7c28-a203-d8507dc8e59b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019fb536-f4be-7c28-a203-d8507dc8e59b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019fb536-f4be-7f61-bcff-c59ae54d5d23" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019fb536-f4be-7f61-bcff-c59ae54d5d23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_019fb536-f4be-720b-a6b7-5a5b0b28cfc1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_AccountsReceivableNet_019fb536-f4be-720b-a6b7-5a5b0b28cfc1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRentReceivablesNet_019fb536-f4be-736b-aec1-c400e6d4f885" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredRentReceivablesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_DeferredRentReceivablesNet_019fb536-f4be-736b-aec1-c400e6d4f885" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCosts_019fb536-f4be-7d06-a4d8-4de7991f8dbe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_DeferredCosts_019fb536-f4be-7d06-a4d8-4de7991f8dbe" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssets_019fb536-f4be-7430-8db3-41dc0e3c25fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssets_019fb536-f4be-7430-8db3-41dc0e3c25fe" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateHeldforsale_019fb536-f4be-7fc5-9267-e645c01fdcff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateHeldforsale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_RealEstateHeldforsale_019fb536-f4be-7fc5-9267-e645c01fdcff" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019fb536-f4be-7bb6-9ee8-df488c5100c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_OperatingLeaseLiability_019fb536-f4be-7bb6-9ee8-df488c5100c9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019fb536-f4be-73e1-aa33-10c171e8aab1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAndNoncurrent_019fb536-f4be-73e1-aa33-10c171e8aab1" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019fb536-f4be-75d9-af63-47fd3e1d1618" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_OtherLiabilities_019fb536-f4be-75d9-af63-47fd3e1d1618" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_019fb536-f4be-7350-834c-939984c0de10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongLivedAssetsHeldForSaleLineItems_019fb536-f4be-7d19-8a1f-c6ac82b026e0" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_019fb536-f4be-7350-834c-939984c0de10" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/RealEstateScheduleofAssetDispositionsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#RealEstateScheduleofAssetDispositionsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/RealEstateScheduleofAssetDispositionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7903-8140-6cd5188d4955" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7903-8140-6cd5188d4955" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7903-8140-6cd5188d4955_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7903-8140-6cd5188d4955" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7903-8140-6cd5188d4955_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7903-8140-6cd5188d4955" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NorthFirstBusinessParkMember_019edbbc-1ec9-76e9-ac76-db7b4f4cb759" xlink:href="bxp-20260630.xsd#bxp_NorthFirstBusinessParkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:to="loc_bxp_NorthFirstBusinessParkMember_019edbbc-1ec9-76e9-ac76-db7b4f4cb759" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ShadyGroveParcelOneMember_019edbbc-1ec9-70d1-81a4-35af7394ad6a" xlink:href="bxp-20260630.xsd#bxp_ShadyGroveParcelOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:to="loc_bxp_ShadyGroveParcelOneMember_019edbbc-1ec9-70d1-81a4-35af7394ad6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TheLoftsAtAtlanticWharfMember_019edbbc-1ec9-785a-86a6-6c7bb8f6b6e3" xlink:href="bxp-20260630.xsd#bxp_TheLoftsAtAtlanticWharfMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:to="loc_bxp_TheLoftsAtAtlanticWharfMember_019edbbc-1ec9-785a-86a6-6c7bb8f6b6e3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_KingstowneRetailMember_019fb54a-35dc-7084-8e2e-6b94df31cefb" xlink:href="bxp-20260630.xsd#bxp_KingstowneRetailMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:to="loc_bxp_KingstowneRetailMember_019fb54a-35dc-7084-8e2e-6b94df31cefb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-7a01-b684-9d4030ddcce2" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsComplexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7fbc-8563-32bc68ef94e9" xlink:to="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-7a01-b684-9d4030ddcce2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-7b94-8a68-e577db7941a8" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-7b94-8a68-e577db7941a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7b94-8a68-e577db7941a8_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7b94-8a68-e577db7941a8" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7b94-8a68-e577db7941a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7a41-8605-9688ba033441" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7b94-8a68-e577db7941a8" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7a41-8605-9688ba033441" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7f63-bae2-a5038371402e" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-7a41-8605-9688ba033441" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1ec9-7f63-bae2-a5038371402e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7fa3-b40a-25fd0f07aad1" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_019edbbc-1ec9-726c-ae3d-674d278d8587" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:to="loc_us-gaap_LandMember_019edbbc-1ec9-726c-ae3d-674d278d8587" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ApartmentBuildingMember_019edbbc-1ec9-72f5-b87e-6be4abd2bee8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ApartmentBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:to="loc_srt_ApartmentBuildingMember_019edbbc-1ec9-72f5-b87e-6be4abd2bee8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RetailSiteMember_019fb54d-1a0a-790f-a56e-85e48b938432" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RetailSiteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:to="loc_srt_RetailSiteMember_019fb54d-1a0a-790f-a56e-85e48b938432" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LandResidentialRetailAndOfficeMember_019edbbc-1ec9-7bbe-bdb9-3f01dc791316" xlink:href="bxp-20260630.xsd#bxp_LandResidentialRetailAndOfficeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:to="loc_bxp_LandResidentialRetailAndOfficeMember_019edbbc-1ec9-7bbe-bdb9-3f01dc791316" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RelatedToPriorPeriodSalesMember_019edbbc-1ec9-7057-8179-b926394912fd" xlink:href="bxp-20260630.xsd#bxp_RelatedToPriorPeriodSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-78f4-9eec-332f1d1dccac" xlink:to="loc_bxp_RelatedToPriorPeriodSalesMember_019edbbc-1ec9-7057-8179-b926394912fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f74-9185-72cba9f41bb0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f74-9185-72cba9f41bb0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7f74-9185-72cba9f41bb0_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f74-9185-72cba9f41bb0" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7f74-9185-72cba9f41bb0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-79fc-9b06-9ea32d462b0b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f74-9185-72cba9f41bb0" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-79fc-9b06-9ea32d462b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7d94-9be6-4bc85ee1230a" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-79fc-9b06-9ea32d462b0b" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7d94-9be6-4bc85ee1230a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1ec9-7c31-aff5-02cfe81711a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019edbbc-1ec9-713d-9a0b-20055e5bf272" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1ec9-7c31-aff5-02cfe81711a7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1ec9-7c31-aff5-02cfe81711a7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1ec9-7c31-aff5-02cfe81711a7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1ec9-7c31-aff5-02cfe81711a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1ec9-7847-8301-9e5b9c48bd5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1ec9-7c31-aff5-02cfe81711a7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1ec9-7847-8301-9e5b9c48bd5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_019edbbc-1ec9-71fc-8274-60480569b061" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LandBuildingsAndImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1ec9-7847-8301-9e5b9c48bd5f" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_019edbbc-1ec9-71fc-8274-60480569b061" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1ec9-7104-a10d-3fd19ca759d9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1ec9-7104-a10d-3fd19ca759d9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ContractualSalePrice_019edbbc-1ec9-7474-a4c4-c00b126f2ab0" xlink:href="bxp-20260630.xsd#bxp_ContractualSalePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_bxp_ContractualSalePrice_019edbbc-1ec9-7474-a4c4-c00b126f2ab0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures_019edbbc-1ec9-77bb-911e-ec8a329a1f34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_ProceedsFromRealEstateAndRealEstateJointVentures_019edbbc-1ec9-77bb-911e-ec8a329a1f34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-78df-8520-a19da2e531f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-78df-8520-a19da2e531f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-71e9-b81c-df4f6aa3e14d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-71e9-b81c-df4f6aa3e14d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019edbbc-1ec9-71e1-b574-708d80fb5bfa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7041-9d92-81b0c4b07417" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_019edbbc-1ec9-71e1-b574-708d80fb5bfa" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/RealEstateNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#RealEstateNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/RealEstateNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7fc0-9b45-c94c61e205c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRealEstatePropertiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7fc0-9b45-c94c61e205c7" xlink:to="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-79dc-bb1a-4a3e192f89ad" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RestonNextRetailMember_019edbbc-1ec9-7a42-85f2-246a219d4cfd" xlink:href="bxp-20260630.xsd#bxp_RestonNextRetailMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:to="loc_bxp_RestonNextRetailMember_019edbbc-1ec9-7a42-85f2-246a219d4cfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoNineZeroBinneyMember_019fb548-14b3-7503-827c-df225365cdb0" xlink:href="bxp-20260630.xsd#bxp_TwoNineZeroBinneyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:to="loc_bxp_TwoNineZeroBinneyMember_019fb548-14b3-7503-827c-df225365cdb0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ReservoirPlaceMember_019fb548-14b3-79a2-a145-5dc6dec5d3d2" xlink:href="bxp-20260630.xsd#bxp_ReservoirPlaceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:to="loc_bxp_ReservoirPlaceMember_019fb548-14b3-79a2-a145-5dc6dec5d3d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumnerSquareMember_019fb548-bc8a-75e4-9f3d-47233a3fb7c9" xlink:href="bxp-20260630.xsd#bxp_SumnerSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-79b0-9a57-170f2c99c9df" xlink:to="loc_bxp_SumnerSquareMember_019fb548-bc8a-75e4-9f3d-47233a3fb7c9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7741-afda-80e6e6e1e80e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7741-afda-80e6e6e1e80e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-7741-afda-80e6e6e1e80e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7741-afda-80e6e6e1e80e" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-7741-afda-80e6e6e1e80e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-76cb-a096-257cbe68dc39" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1ec9-7741-afda-80e6e6e1e80e" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-76cb-a096-257cbe68dc39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RetailSiteMember_019edbbc-1ec9-7dfc-bcca-0584e2066fa1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RetailSiteMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1ec9-76cb-a096-257cbe68dc39" xlink:to="loc_srt_RetailSiteMember_019edbbc-1ec9-7dfc-bcca-0584e2066fa1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb548-14b3-7147-8f80-6be916acd011" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb548-14b3-7147-8f80-6be916acd011" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb548-14b3-7147-8f80-6be916acd011_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb548-14b3-7147-8f80-6be916acd011" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb548-14b3-7147-8f80-6be916acd011_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb548-14b3-7382-a953-7d93630ecd0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019fb548-14b3-7147-8f80-6be916acd011" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb548-14b3-7382-a953-7d93630ecd0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019fb548-14b3-7ea3-b5cc-9259b26aed43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019fb548-14b3-7382-a953-7d93630ecd0f" xlink:to="loc_us-gaap_ConstructionInProgressMember_019fb548-14b3-7ea3-b5cc-9259b26aed43" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019fc973-744a-7efb-9b48-773a58bbe03e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRealEstatePropertiesTable_019edbbc-1ec9-7e19-917e-a1b1ca00085d" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019fc973-744a-7efb-9b48-773a58bbe03e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019fc973-744a-7efb-9b48-773a58bbe03e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019fc973-744a-7efb-9b48-773a58bbe03e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019fc973-744a-7efb-9b48-773a58bbe03e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019fc973-744a-7673-9803-9deebdbf1009" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019fc973-744a-7efb-9b48-773a58bbe03e" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019fc973-744a-7673-9803-9deebdbf1009" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019fc974-0ac0-797d-a622-b67c963d9089" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019fc973-744a-7673-9803-9deebdbf1009" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019fc974-0ac0-797d-a622-b67c963d9089" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1ec9-78e3-a5a6-f11d7ce6f0d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7fc0-9b45-c94c61e205c7" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1ec9-78e3-a5a6-f11d7ce6f0d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LongLivedAssetHeldForSaleTermOfDisposal_019fc82f-c0b2-7a40-b99e-50d1e6837c62" xlink:href="bxp-20260630.xsd#bxp_LongLivedAssetHeldForSaleTermOfDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7fc0-9b45-c94c61e205c7" xlink:to="loc_bxp_LongLivedAssetHeldForSaleTermOfDisposal_019fc82f-c0b2-7a40-b99e-50d1e6837c62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityOwnershipPercentage_019fc972-7a1e-796f-b84d-d1c5480c4179" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableInterestEntityOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesLineItems_019edbbc-1ec9-7fc0-9b45-c94c61e205c7" xlink:to="loc_us-gaap_VariableInterestEntityOwnershipPercentage_019fc972-7a1e-796f-b84d-d1c5480c4179" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesInvestmentsinUnconsolidatedJointVenturesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesInvestmentsinUnconsolidatedJointVenturesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesInvestmentsinUnconsolidatedJointVenturesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7a60-8843-015da7eb2dda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7a60-8843-015da7eb2dda" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7cfd-9229-ef149067beb9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7a60-8843-015da7eb2dda" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7cfd-9229-ef149067beb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7cfd-9229-ef149067beb9_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7cfd-9229-ef149067beb9" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7cfd-9229-ef149067beb9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7cfd-9229-ef149067beb9" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_WpProjectDeveloperLlcMember_019edbbc-1ec9-7955-8925-0e5a69ed0207" xlink:href="bxp-20260630.xsd#bxp_WpProjectDeveloperLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_WpProjectDeveloperLlcMember_019edbbc-1ec9-7955-8925-0e5a69ed0207" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FiveZeroZeroNorthCapitolLlcMember_019edbbc-1ec9-7bd1-bd1c-31bcf5637109" xlink:href="bxp-20260630.xsd#bxp_FiveZeroZeroNorthCapitolLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_FiveZeroZeroNorthCapitolLlcMember_019edbbc-1ec9-7bd1-bd1c-31bcf5637109" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FivezerooneKStreetLLCMember_019edbbc-1ec9-7ce5-b0d9-3c18f892a54a" xlink:href="bxp-20260630.xsd#bxp_FivezerooneKStreetLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_FivezerooneKStreetLLCMember_019edbbc-1ec9-7ce5-b0d9-3c18f892a54a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PodiumVentureLLCMember_019edbbc-1ec9-7dc3-9c4c-de238864a5f9" xlink:href="bxp-20260630.xsd#bxp_PodiumVentureLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_PodiumVentureLLCMember_019edbbc-1ec9-7dc3-9c4c-de238864a5f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ResidentialTowerDeveloperLLCMember_019edbbc-1ec9-7f26-befa-a1d45d113e96" xlink:href="bxp-20260630.xsd#bxp_ResidentialTowerDeveloperLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_ResidentialTowerDeveloperLLCMember_019edbbc-1ec9-7f26-befa-a1d45d113e96" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_HotelTowerDeveloperLLCMember_019edbbc-1ec9-7593-afcc-769ace95842a" xlink:href="bxp-20260630.xsd#bxp_HotelTowerDeveloperLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_HotelTowerDeveloperLLCMember_019edbbc-1ec9-7593-afcc-769ace95842a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OfficeVentureLLCMember_019edbbc-1ec9-71fc-bb31-a274c9639ef5" xlink:href="bxp-20260630.xsd#bxp_OfficeVentureLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_OfficeVentureLLCMember_019edbbc-1ec9-71fc-bb31-a274c9639ef5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OneTwoSixFiveMainOfficeJVLLCMember_019edbbc-1ec9-773d-8146-e902ce2d348f" xlink:href="bxp-20260630.xsd#bxp_OneTwoSixFiveMainOfficeJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_OneTwoSixFiveMainOfficeJVLLCMember_019edbbc-1ec9-773d-8146-e902ce2d348f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BNYTowerHoldingsLLCMember_019edbbc-1ec9-7690-ace0-ed7f8e6f39fa" xlink:href="bxp-20260630.xsd#bxp_BNYTowerHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_BNYTowerHoldingsLLCMember_019edbbc-1ec9-7690-ace0-ed7f8e6f39fa" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CAColoradoCenterLLCMember_019edbbc-1ec9-74de-b203-db664a75a6a1" xlink:href="bxp-20260630.xsd#bxp_CAColoradoCenterLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_CAColoradoCenterLLCMember_019edbbc-1ec9-74de-b203-db664a75a6a1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-7d5b-ba59-925e1a20837e" xlink:href="bxp-20260630.xsd#bxp_SevensevenfivezeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-7d5b-ba59-925e1a20837e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BPM3HBVentureLLCMember_019edbbc-1ec9-7d88-83fb-3010ba009fdc" xlink:href="bxp-20260630.xsd#bxp_BPM3HBVentureLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_BPM3HBVentureLLCMember_019edbbc-1ec9-7d88-83fb-3010ba009fdc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PlatformSixteenMember_019edbbc-1ec9-79a6-a88c-62fbcf8d0efd" xlink:href="bxp-20260630.xsd#bxp_PlatformSixteenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_PlatformSixteenMember_019edbbc-1ec9-79a6-a88c-62fbcf8d0efd" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7e06-845e-ee1c6634eb01" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7e06-845e-ee1c6634eb01" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RosecransSepulvedaPartnersFourLLCMember_019edbbc-1ec9-7674-942a-742d9b5c3fd7" xlink:href="bxp-20260630.xsd#bxp_RosecransSepulvedaPartnersFourLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_RosecransSepulvedaPartnersFourLLCMember_019edbbc-1ec9-7674-942a-742d9b5c3fd7" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPlazaREITLLCMember_019edbbc-1ec9-7180-a776-efcfc5a911cf" xlink:href="bxp-20260630.xsd#bxp_SafecoPlazaREITLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_SafecoPlazaREITLLCMember_019edbbc-1ec9-7180-a776-efcfc5a911cf" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPartnerEntityOneMember_019edbbc-1ec9-7bfa-b9c4-af00c9b5ca6b" xlink:href="bxp-20260630.xsd#bxp_SafecoPartnerEntityOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_SafecoPartnerEntityOneMember_019edbbc-1ec9-7bfa-b9c4-af00c9b5ca6b" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeSixZeroPASHoldcoLLCMember_019edbbc-1ec9-7238-8c53-259bbb493aaf" xlink:href="bxp-20260630.xsd#bxp_ThreeSixZeroPASHoldcoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_ThreeSixZeroPASHoldcoLLCMember_019edbbc-1ec9-7238-8c53-259bbb493aaf" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PRIIBXPRestonGatewayLLCMember_019edbbc-1ec9-778a-9f07-778936718e8d" xlink:href="bxp-20260630.xsd#bxp_PRIIBXPRestonGatewayLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_PRIIBXPRestonGatewayLLCMember_019edbbc-1ec9-778a-9f07-778936718e8d" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoZeroZeroFifthAvenueJVLLCMember_019edbbc-1ec9-77df-af47-73b8b07a275d" xlink:href="bxp-20260630.xsd#bxp_TwoZeroZeroFifthAvenueJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_TwoZeroZeroFifthAvenueJVLLCMember_019edbbc-1ec9-77df-af47-73b8b07a275d" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ABXPWorldgateInvestmentsLLCMember_019edbbc-1ec9-7000-a38f-7254aa7b238f" xlink:href="bxp-20260630.xsd#bxp_ABXPWorldgateInvestmentsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_ABXPWorldgateInvestmentsLLCMember_019edbbc-1ec9-7000-a38f-7254aa7b238f" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CAB290ColesVentureLLCMember_019edbbc-1ec9-7fb7-93ae-d95d8c0303d8" xlink:href="bxp-20260630.xsd#bxp_CAB290ColesVentureLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_CAB290ColesVentureLLCMember_019edbbc-1ec9-7fb7-93ae-d95d8c0303d8" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CAB290ColesHoldcoLLCMember_019edbbc-1ec9-7785-94eb-0fe0bbd2c9f0" xlink:href="bxp-20260630.xsd#bxp_CAB290ColesHoldcoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_CAB290ColesHoldcoLLCMember_019edbbc-1ec9-7785-94eb-0fe0bbd2c9f0" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SeventeenHartwellJVLLCMember_019edbbc-1ec9-7eca-aacd-269a7b21acc5" xlink:href="bxp-20260630.xsd#bxp_SeventeenHartwellJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_SeventeenHartwellJVLLCMember_019edbbc-1ec9-7eca-aacd-269a7b21acc5" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-71c8-9d68-2283299ca11c" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-71c8-9d68-2283299ca11c" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EntityOwningLandAndInfrastructureOfProjectMember_019edbbc-1ec9-73b6-92f2-ebab6eefe53b" xlink:href="bxp-20260630.xsd#bxp_EntityOwningLandAndInfrastructureOfProjectMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_EntityOwningLandAndInfrastructureOfProjectMember_019edbbc-1ec9-73b6-92f2-ebab6eefe53b" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPartnerEntityTwoMember_019edbbc-1ec9-7224-b851-2e4156a0f3de" xlink:href="bxp-20260630.xsd#bxp_SafecoPartnerEntityTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_SafecoPartnerEntityTwoMember_019edbbc-1ec9-7224-b851-2e4156a0f3de" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeSixZeroPASHoldcoLLCIndirectOwnershipMember_019edbbc-1ec9-7abf-8204-288fb78cef49" xlink:href="bxp-20260630.xsd#bxp_ThreeSixZeroPASHoldcoLLCIndirectOwnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_ThreeSixZeroPASHoldcoLLCIndirectOwnershipMember_019edbbc-1ec9-7abf-8204-288fb78cef49" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeSixZeroParkAvenueSouthPartnersEntityOneMember_019edbbc-1ec9-7859-b8a5-efdee5c64706" xlink:href="bxp-20260630.xsd#bxp_ThreeSixZeroParkAvenueSouthPartnersEntityOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_ThreeSixZeroParkAvenueSouthPartnersEntityOneMember_019edbbc-1ec9-7859-b8a5-efdee5c64706" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_WorldgateMultifamilyJVLLCMember_019fb919-9f77-7eed-96a7-f5cc234a609b" xlink:href="bxp-20260630.xsd#bxp_WorldgateMultifamilyJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-780f-b867-172334655851" xlink:to="loc_bxp_WorldgateMultifamilyJVLLCMember_019fb919-9f77-7eed-96a7-f5cc234a609b" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1ec9-7a93-9541-2a4524da669e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7a60-8843-015da7eb2dda" xlink:to="loc_srt_OwnershipAxis_019edbbc-1ec9-7a93-9541-2a4524da669e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-7a93-9541-2a4524da669e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-7a93-9541-2a4524da669e" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-7a93-9541-2a4524da669e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-7aca-85b6-f1cfabbbe76b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-7a93-9541-2a4524da669e" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-7aca-85b6-f1cfabbbe76b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-79e7-a2ee-da61064e332c" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-7aca-85b6-f1cfabbbe76b" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-79e7-a2ee-da61064e332c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019edbbc-1ec9-775d-9192-fa20c8c32729" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7a60-8843-015da7eb2dda" xlink:to="loc_srt_RangeAxis_019edbbc-1ec9-775d-9192-fa20c8c32729" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1ec9-775d-9192-fa20c8c32729_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019edbbc-1ec9-775d-9192-fa20c8c32729" xlink:to="loc_srt_RangeMember_019edbbc-1ec9-775d-9192-fa20c8c32729_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1ec9-71a6-a1ed-8d0cd993b9d2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019edbbc-1ec9-775d-9192-fa20c8c32729" xlink:to="loc_srt_RangeMember_019edbbc-1ec9-71a6-a1ed-8d0cd993b9d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019edbbc-1ec9-7527-baa1-6509ee513a97" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1ec9-71a6-a1ed-8d0cd993b9d2" xlink:to="loc_srt_MaximumMember_019edbbc-1ec9-7527-baa1-6509ee513a97" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NameOfJointVentureProperty_019edbbc-1ec9-7a8e-a51d-31b8ccb52c30" xlink:href="bxp-20260630.xsd#bxp_NameOfJointVentureProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_bxp_NameOfJointVentureProperty_019edbbc-1ec9-7a8e-a51d-31b8ccb52c30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-760d-a5e4-2b10fb9d0451" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-760d-a5e4-2b10fb9d0451" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019edbbc-1ec9-7d46-b90b-79409d9623e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_OtherLiabilities_019edbbc-1ec9-7d46-b90b-79409d9623e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1ec9-732b-8746-a46f8e109c0d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1ec9-732b-8746-a46f8e109c0d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesnet_019edbbc-1ec9-7130-90f6-07bd6b54caab" xlink:href="bxp-20260630.xsd#bxp_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesnet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_bxp_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVenturesnet_019edbbc-1ec9-7130-90f6-07bd6b54caab" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019edbbc-1ec9-7acc-90a0-aa6877352907" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019edbbc-1ec9-7acc-90a0-aa6877352907" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InternalRateOfReturnOnPreferredEquity_019edbbc-1ec9-78ba-b8a5-19af27829ac3" xlink:href="bxp-20260630.xsd#bxp_InternalRateOfReturnOnPreferredEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_bxp_InternalRateOfReturnOnPreferredEquity_019edbbc-1ec9-78ba-b8a5-19af27829ac3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1ec9-74e5-a584-437776d5922e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1ec9-74e5-a584-437776d5922e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ContractualSalePrice_019edbbc-1ec9-7da6-901f-b8a2c74d34d7" xlink:href="bxp-20260630.xsd#bxp_ContractualSalePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_bxp_ContractualSalePrice_019edbbc-1ec9-7da6-901f-b8a2c74d34d7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1ec9-7861-a887-9c0df7c7ea8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1ec9-7861-a887-9c0df7c7ea8f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-777c-8ef4-74e7d2e099a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7daa-9526-00ca653d3ac7" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-777c-8ef4-74e7d2e099a0" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesBalanceSheetsoftheUnconsolidatedJointVenturesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesBalanceSheetsoftheUnconsolidatedJointVenturesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesBalanceSheetsoftheUnconsolidatedJointVenturesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7d5d-a3c2-cad7dd9b22c6" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CAColoradoCenterLLCMember_019edbbc-1ec9-7ab7-8f57-8fe215febe1b" xlink:href="bxp-20260630.xsd#bxp_CAColoradoCenterLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_CAColoradoCenterLLCMember_019edbbc-1ec9-7ab7-8f57-8fe215febe1b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoZeroZeroFifthAvenueJVLLCMember_019edbbc-1ec9-75cb-88f5-fb8c0a9d7d71" xlink:href="bxp-20260630.xsd#bxp_TwoZeroZeroFifthAvenueJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_TwoZeroZeroFifthAvenueJVLLCMember_019edbbc-1ec9-75cb-88f5-fb8c0a9d7d71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPlazaREITLLCMember_019edbbc-1ec9-7a84-a981-f906fd119ef2" xlink:href="bxp-20260630.xsd#bxp_SafecoPlazaREITLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_SafecoPlazaREITLLCMember_019edbbc-1ec9-7a84-a981-f906fd119ef2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-7081-8b5d-9ff5a77b65e7" xlink:href="bxp-20260630.xsd#bxp_SevensevenfivezeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-7081-8b5d-9ff5a77b65e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-7fb6-8745-7a268c3238e2" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsComplexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-7fb6-8745-7a268c3238e2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BNYTowerHoldingsLLCMember_019edbbc-1ec9-7df1-bea1-31d81733a5e5" xlink:href="bxp-20260630.xsd#bxp_BNYTowerHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_BNYTowerHoldingsLLCMember_019edbbc-1ec9-7df1-bea1-31d81733a5e5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeSixZeroPASHoldcoLLCMember_019edbbc-1ec9-7d2d-b77e-e084a492a177" xlink:href="bxp-20260630.xsd#bxp_ThreeSixZeroPASHoldcoLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_ThreeSixZeroPASHoldcoLLCMember_019edbbc-1ec9-7d2d-b77e-e084a492a177" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PlatformSixteenMember_019edbbc-1ec9-7c76-a1f7-43a47f8b162f" xlink:href="bxp-20260630.xsd#bxp_PlatformSixteenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_PlatformSixteenMember_019edbbc-1ec9-7c76-a1f7-43a47f8b162f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RemainingOtherInvestmentMember_019edbbc-1ec9-7f76-b8c9-751d1a8e5cdc" xlink:href="bxp-20260630.xsd#bxp_RemainingOtherInvestmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_RemainingOtherInvestmentMember_019edbbc-1ec9-7f76-b8c9-751d1a8e5cdc" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OtherUnconsolidatedJVSMember_019edbbc-1ec9-7379-a6f2-6bf29a0225d4" xlink:href="bxp-20260630.xsd#bxp_OtherUnconsolidatedJVSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_OtherUnconsolidatedJVSMember_019edbbc-1ec9-7379-a6f2-6bf29a0225d4" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7e3a-b92f-3a7cf133977f" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7a48-b36e-539b2ae5ee13" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7e3a-b92f-3a7cf133977f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7287-b098-c289363e2aab" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7811-bfd2-e5e771ca2cc5" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7287-b098-c289363e2aab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-703c-81ab-45067eda244f" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-7287-b098-c289363e2aab" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-703c-81ab-45067eda244f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7997-b3b6-fa121303617a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7997-b3b6-fa121303617a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7997-b3b6-fa121303617a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7997-b3b6-fa121303617a" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7997-b3b6-fa121303617a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7907-a7b5-f8c80f50b588" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7997-b3b6-fa121303617a" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7907-a7b5-f8c80f50b588" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-700d-8705-84b713af8c51" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsComplexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7907-a7b5-f8c80f50b588" xlink:to="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-700d-8705-84b713af8c51" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPlazaMember_019edbbc-1ec9-7d50-bc66-41ca34043dc7" xlink:href="bxp-20260630.xsd#bxp_SafecoPlazaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7907-a7b5-f8c80f50b588" xlink:to="loc_bxp_SafecoPlazaMember_019edbbc-1ec9-7d50-bc66-41ca34043dc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7008-b105-b4c0e041c0b1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77ae-a8d3-f7c6f26016ab" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7008-b105-b4c0e041c0b1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7008-b105-b4c0e041c0b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7008-b105-b4c0e041c0b1" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7008-b105-b4c0e041c0b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7953-aa5c-3f4fbaf22490" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7008-b105-b4c0e041c0b1" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7953-aa5c-3f4fbaf22490" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7c0a-9582-fe3356440e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7953-aa5c-3f4fbaf22490" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7c0a-9582-fe3356440e7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019edbbc-1ec9-787a-a227-14913525d20e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_AssetsAbstract_019edbbc-1ec9-787a-a227-14913525d20e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1ec9-7ccc-8bc7-e531d510a2ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1ec9-787a-a227-14913525d20e" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019edbbc-1ec9-7ccc-8bc7-e531d510a2ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019edbbc-1ec9-7cf9-8614-69e862507f34" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1ec9-787a-a227-14913525d20e" xlink:to="loc_us-gaap_OtherAssets_019edbbc-1ec9-7cf9-8614-69e862507f34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019edbbc-1ec9-7072-8258-d3894be38bd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019edbbc-1ec9-787a-a227-14913525d20e" xlink:to="loc_us-gaap_Assets_019edbbc-1ec9-7072-8258-d3894be38bd9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebt_019edbbc-1ec9-720f-960a-00c7c07a25e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:to="loc_us-gaap_SecuredDebt_019edbbc-1ec9-720f-960a-00c7c07a25e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019edbbc-1ec9-77be-ac3c-a58385d93652" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:to="loc_us-gaap_OtherLiabilities_019edbbc-1ec9-77be-ac3c-a58385d93652" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019edbbc-1ec9-71a5-b266-2c1d3dee7092" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:to="loc_us-gaap_StockholdersEquity_019edbbc-1ec9-71a5-b266-2c1d3dee7092" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019edbbc-1ec9-78a7-8db0-fcb905e16efa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019edbbc-1ec9-7730-935d-d902170d78d0" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019edbbc-1ec9-78a7-8db0-fcb905e16efa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanyShareOfEquity_019edbbc-1ec9-756c-bab0-7412e70a68c8" xlink:href="bxp-20260630.xsd#bxp_CompanyShareOfEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_bxp_CompanyShareOfEquity_019edbbc-1ec9-756c-bab0-7412e70a68c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity_019edbbc-1ec9-7cd4-ad64-74e352b491ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity_019edbbc-1ec9-7cd4-ad64-74e352b491ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1ec9-744c-b746-6ff05dc09b1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures_019edbbc-1ec9-744c-b746-6ff05dc09b1f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1ec9-70fa-a4ad-88a4457fb3ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019edbbc-1ec9-70fa-a4ad-88a4457fb3ed" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeLeaseLeaseReceivable_019edbbc-1ec9-700c-9f9f-c316ccd4fce1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeLeaseLeaseReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_SalesTypeLeaseLeaseReceivable_019edbbc-1ec9-700c-9f9f-c316ccd4fce1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019edbbc-1ec9-76b9-a87f-441bd9e623a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_OperatingLeaseLiability_019edbbc-1ec9-76b9-a87f-441bd9e623a6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-791a-bd43-b343e85d3de0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-791a-bd43-b343e85d3de0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019edbbc-1ec9-7e91-ba58-b5a066b7f15d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-72bd-8806-2b0772e50b9a" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_019edbbc-1ec9-7e91-ba58-b5a066b7f15d" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7321-bcdd-4742c84b1b47_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7321-bcdd-4742c84b1b47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7ed0-a44d-3ef605f87ff4" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7ed0-a44d-3ef605f87ff4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-752e-a1c5-50031951a1e4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-752e-a1c5-50031951a1e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-7928-b534-daa2b0b21e15" xlink:href="bxp-20260630.xsd#bxp_JointVenturePartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:to="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-7928-b534-daa2b0b21e15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-7f55-8d55-d81d0d15ba19" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-7f55-8d55-d81d0d15ba19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7678-a474-cc35a5dcde07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7678-a474-cc35a5dcde07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019edbbc-1ec9-7204-bd71-57f01554e7a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019edbbc-1ec9-7204-bd71-57f01554e7a1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-73d7-9ae3-b024a19a661a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-73d7-9ae3-b024a19a661a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7189-beda-86098d60db04" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7189-beda-86098d60db04" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-70f5-ad05-4cae496060bf" xlink:href="bxp-20260630.xsd#bxp_SevensevenfivezeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:to="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-70f5-ad05-4cae496060bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019edbbc-1ec9-75d9-9c0d-fcbd21a8ae21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_Revenues_019edbbc-1ec9-75d9-9c0d-fcbd21a8ae21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019edbbc-1ec9-7e6f-bea2-84cfaac7f1a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_OperatingExpenses_019edbbc-1ec9-7e6f-bea2-84cfaac7f1a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1ec9-77da-acf8-2b5f7ff9cd2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1ec9-77da-acf8-2b5f7ff9cd2b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019edbbc-1ec9-776d-8bbb-5868804e906b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_DepreciationAndAmortization_019edbbc-1ec9-776d-8bbb-5868804e906b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019edbbc-1ec9-7f1f-89e5-47e36b1efba4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_CostsAndExpenses_019edbbc-1ec9-7f1f-89e5-47e36b1efba4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1ec9-7e72-8e72-c79660591d92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1ec9-7e72-8e72-c79660591d92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019edbbc-1ec9-7b15-b6ef-5df6427412ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_InterestExpense_019edbbc-1ec9-7b15-b6ef-5df6427412ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfDerivatives_019fb92d-c004-7dfe-8b98-926d6fc8aaf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnSaleOfDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainLossOnSaleOfDerivatives_019fb92d-c004-7dfe-8b98-926d6fc8aaf7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019edbbc-1ec9-7698-b6ee-5c72b325196e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019edbbc-1ec9-7698-b6ee-5c72b325196e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1ec9-708a-957e-7fea24c53c28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1ec9-708a-957e-7fea24c53c28" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-7eb8-b6cf-40c50805fbd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-7eb8-b6cf-40c50805fbd2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-7b73-8206-cbc8c30587ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-7b73-8206-cbc8c30587ee" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1ec9-724f-ac35-3c5f09ec12f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1ec9-724f-ac35-3c5f09ec12f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareOfNetIncomeLoss_019edbbc-1ec9-77cf-afc4-568d4310873b" xlink:href="bxp-20260630.xsd#bxp_CompanysShareOfNetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_CompanysShareOfNetIncomeLoss_019edbbc-1ec9-77cf-afc4-568d4310873b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GainOnUnconsolidatedJointVentureInvestment_019edbbc-1ec9-7cfc-88c7-445968c14e11" xlink:href="bxp-20260630.xsd#bxp_GainOnUnconsolidatedJointVentureInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_GainOnUnconsolidatedJointVentureInvestment_019edbbc-1ec9-7cfc-88c7-445968c14e11" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-7ec0-8550-2fd190d34ecf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-7ec0-8550-2fd190d34ecf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_IncomeStatementBasisDifferential_019edbbc-1ec9-759f-abe5-869818a1db4c" xlink:href="bxp-20260630.xsd#bxp_IncomeStatementBasisDifferential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_IncomeStatementBasisDifferential_019edbbc-1ec9-759f-abe5-869818a1db4c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1ec9-7ae1-b673-e27610c8c767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1ec9-7ae1-b673-e27610c8c767" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StraightLineRentAdjustments_019edbbc-1ec9-7164-a40c-25ba0f6876a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StraightLineRentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_StraightLineRentAdjustments_019edbbc-1ec9-7164-a40c-25ba0f6876a9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c6e-8ddd-9fdf32fce58e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c6e-8ddd-9fdf32fce58e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1ec9-7109-be73-59e86e968a51" xlink:href="bxp-20260630.xsd#bxp_AboveAndBelowMarketRentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1ec9-7109-be73-59e86e968a51" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfInvestments_019edbbc-1ec9-7d2c-9767-05eb12bbc012" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ImpairmentOfInvestments_019edbbc-1ec9-7d2c-9767-05eb12bbc012" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails_1" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails_1"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesStatementsofOperationsoftheJointVenturesDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7321-bcdd-4742c84b1b47_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7321-bcdd-4742c84b1b47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7321-bcdd-4742c84b1b47" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7ed0-a44d-3ef605f87ff4" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-7499-96c4-0cc8842236b7" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-7ed0-a44d-3ef605f87ff4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-752e-a1c5-50031951a1e4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-752e-a1c5-50031951a1e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-752e-a1c5-50031951a1e4" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-7928-b534-daa2b0b21e15" xlink:href="bxp-20260630.xsd#bxp_JointVenturePartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:to="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-7928-b534-daa2b0b21e15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-7f55-8d55-d81d0d15ba19" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-783a-b8a1-070d243b6350" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-7f55-8d55-d81d0d15ba19" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7fab-b7bc-1d65cb8f207e" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7678-a474-cc35a5dcde07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7cbd-b043-47641d05c93c" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-7678-a474-cc35a5dcde07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-77b5-96af-e338120b61dd" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-73d7-9ae3-b024a19a661a_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-73d7-9ae3-b024a19a661a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-73d7-9ae3-b024a19a661a" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7189-beda-86098d60db04" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7189-beda-86098d60db04" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-70f5-ad05-4cae496060bf" xlink:href="bxp-20260630.xsd#bxp_SevensevenfivezeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-78de-84e5-7e2029b3e848" xlink:to="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-70f5-ad05-4cae496060bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019edbbc-1ec9-75d9-9c0d-fcbd21a8ae21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_Revenues_019edbbc-1ec9-75d9-9c0d-fcbd21a8ae21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019edbbc-1ec9-7e6f-bea2-84cfaac7f1a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_OperatingExpenses_019edbbc-1ec9-7e6f-bea2-84cfaac7f1a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1ec9-77da-acf8-2b5f7ff9cd2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1ec9-77da-acf8-2b5f7ff9cd2b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019edbbc-1ec9-776d-8bbb-5868804e906b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_DepreciationAndAmortization_019edbbc-1ec9-776d-8bbb-5868804e906b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019edbbc-1ec9-7f1f-89e5-47e36b1efba4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019edbbc-1ec9-7c77-82dd-24147e6e384b" xlink:to="loc_us-gaap_CostsAndExpenses_019edbbc-1ec9-7f1f-89e5-47e36b1efba4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1ec9-7e72-8e72-c79660591d92" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1ec9-7e72-8e72-c79660591d92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019edbbc-1ec9-7b15-b6ef-5df6427412ce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_InterestExpense_019edbbc-1ec9-7b15-b6ef-5df6427412ce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfDerivatives_019fb92d-c004-7dfe-8b98-926d6fc8aaf7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnSaleOfDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainLossOnSaleOfDerivatives_019fb92d-c004-7dfe-8b98-926d6fc8aaf7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnDerivatives_019edbbc-1ec9-7698-b6ee-5c72b325196e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnDerivatives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_UnrealizedGainLossOnDerivatives_019edbbc-1ec9-7698-b6ee-5c72b325196e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1ec9-708a-957e-7fea24c53c28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1ec9-708a-957e-7fea24c53c28" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-7eb8-b6cf-40c50805fbd2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1ec9-7eb8-b6cf-40c50805fbd2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-7b73-8206-cbc8c30587ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfRealEstate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019edbbc-1ec9-7b34-bf49-6bbd565bb868" xlink:to="loc_us-gaap_ImpairmentOfRealEstate_019edbbc-1ec9-7b73-8206-cbc8c30587ee" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1ec9-724f-ac35-3c5f09ec12f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1ec9-724f-ac35-3c5f09ec12f2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareOfNetIncomeLoss_019edbbc-1ec9-77cf-afc4-568d4310873b" xlink:href="bxp-20260630.xsd#bxp_CompanysShareOfNetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_CompanysShareOfNetIncomeLoss_019edbbc-1ec9-77cf-afc4-568d4310873b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GainOnUnconsolidatedJointVentureInvestment_019edbbc-1ec9-7cfc-88c7-445968c14e11" xlink:href="bxp-20260630.xsd#bxp_GainOnUnconsolidatedJointVentureInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_GainOnUnconsolidatedJointVentureInvestment_019edbbc-1ec9-7cfc-88c7-445968c14e11" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-7ec0-8550-2fd190d34ecf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-7ec0-8550-2fd190d34ecf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_IncomeStatementBasisDifferential_019edbbc-1ec9-759f-abe5-869818a1db4c" xlink:href="bxp-20260630.xsd#bxp_IncomeStatementBasisDifferential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_IncomeStatementBasisDifferential_019edbbc-1ec9-759f-abe5-869818a1db4c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1ec9-7ae1-b673-e27610c8c767" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1ec9-7ae1-b673-e27610c8c767" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StraightLineRentAdjustments_019edbbc-1ec9-7164-a40c-25ba0f6876a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StraightLineRentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_StraightLineRentAdjustments_019edbbc-1ec9-7164-a40c-25ba0f6876a9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c6e-8ddd-9fdf32fce58e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c6e-8ddd-9fdf32fce58e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1ec9-7109-be73-59e86e968a51" xlink:href="bxp-20260630.xsd#bxp_AboveAndBelowMarketRentAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_bxp_AboveAndBelowMarketRentAdjustments_019edbbc-1ec9-7109-be73-59e86e968a51" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfInvestments_019edbbc-1ec9-7d2c-9767-05eb12bbc012" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7fa8-9b68-b9fe1c4aab10" xlink:to="loc_us-gaap_ImpairmentOfInvestments_019edbbc-1ec9-7d2c-9767-05eb12bbc012" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesScheduleofEquityMethodInvestmentDisposalsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentsinUnconsolidatedJointVenturesScheduleofEquityMethodInvestmentDisposalsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentsinUnconsolidatedJointVenturesScheduleofEquityMethodInvestmentDisposalsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7f5c-99ea-8977f3bb0dde" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7249-b5a4-c5efee86e1a5" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCMember_019edbbc-1ec9-7249-b5a4-c5efee86e1a5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-760d-812a-c00565983e01" xlink:href="bxp-20260630.xsd#bxp_SevensevenfivezeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_SevensevenfivezeroWisconsinAvenueLLCMember_019edbbc-1ec9-760d-812a-c00565983e01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayPortfolioHoldingsLLCAndSevenSevenFiveZeroWisconsinAvenueLLCMember_019edbbc-1ec9-72da-81c3-fe36e2bafb76" xlink:href="bxp-20260630.xsd#bxp_GatewayPortfolioHoldingsLLCAndSevenSevenFiveZeroWisconsinAvenueLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_GatewayPortfolioHoldingsLLCAndSevenSevenFiveZeroWisconsinAvenueLLCMember_019edbbc-1ec9-72da-81c3-fe36e2bafb76" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OneThreeOneFiveZeroWorldgateDriveMember_019fc320-e665-7ff8-82b1-204005655588" xlink:href="bxp-20260630.xsd#bxp_OneThreeOneFiveZeroWorldgateDriveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_OneThreeOneFiveZeroWorldgateDriveMember_019fc320-e665-7ff8-82b1-204005655588" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ABXPWorldgateInvestmentsLLCMember_019fc322-7c93-7b2d-b173-c5f0fe1a19f1" xlink:href="bxp-20260630.xsd#bxp_ABXPWorldgateInvestmentsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_ABXPWorldgateInvestmentsLLCMember_019fc322-7c93-7b2d-b173-c5f0fe1a19f1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevenFiveOneGatewayBoulevardMember_019fc326-304f-7f12-8dab-7b9df5a4ec43" xlink:href="bxp-20260630.xsd#bxp_SevenFiveOneGatewayBoulevardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_SevenFiveOneGatewayBoulevardMember_019fc326-304f-7f12-8dab-7b9df5a4ec43" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_A751GatewayHoldingsLLCMember_019fc327-379f-7fb2-a7ed-9e0a13964dd7" xlink:href="bxp-20260630.xsd#bxp_A751GatewayHoldingsLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7b80-9179-046c9c773643" xlink:to="loc_bxp_A751GatewayHoldingsLLCMember_019fc327-379f-7fb2-a7ed-9e0a13964dd7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7938-ad67-68d056265269" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7938-ad67-68d056265269" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7938-ad67-68d056265269_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7938-ad67-68d056265269" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7938-ad67-68d056265269_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-756c-b848-c6f234992f08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7938-ad67-68d056265269" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-756c-b848-c6f234992f08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-727f-9547-28424ea27c49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-756c-b848-c6f234992f08" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-727f-9547-28424ea27c49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1ec9-7275-a601-15633fe464de" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:to="loc_srt_OwnershipAxis_019edbbc-1ec9-7275-a601-15633fe464de" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-7275-a601-15633fe464de_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-7275-a601-15633fe464de" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-7275-a601-15633fe464de_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-761a-9241-280474f1f0d7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-7275-a601-15633fe464de" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-761a-9241-280474f1f0d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-74d8-914b-e498db2a2116" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-761a-9241-280474f1f0d7" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-74d8-914b-e498db2a2116" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7ea4-b8a9-f488eab627cb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7257-ad6f-e42f050f7c68" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7ea4-b8a9-f488eab627cb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7ea4-b8a9-f488eab627cb_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7ea4-b8a9-f488eab627cb" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7ea4-b8a9-f488eab627cb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7e2a-a652-86c7a854db20" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7ea4-b8a9-f488eab627cb" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7e2a-a652-86c7a854db20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevenSevenFiveZeroWisconsinAvenueMember_019edbbc-1ec9-7063-842b-2fce1b7c3ee8" xlink:href="bxp-20260630.xsd#bxp_SevenSevenFiveZeroWisconsinAvenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7e2a-a652-86c7a854db20" xlink:to="loc_bxp_SevenSevenFiveZeroWisconsinAvenueMember_019edbbc-1ec9-7063-842b-2fce1b7c3ee8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-775f-9e64-02ad21d6f5a0" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsComplexMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7e2a-a652-86c7a854db20" xlink:to="loc_bxp_GatewayCommonsComplexMember_019edbbc-1ec9-775f-9e64-02ad21d6f5a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_GatewayCommonsAndSevenSevenFiveZeroWisconsinAvenueMember_019edbbc-1ec9-7110-909e-a243c34ccba5" xlink:href="bxp-20260630.xsd#bxp_GatewayCommonsAndSevenSevenFiveZeroWisconsinAvenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7e2a-a652-86c7a854db20" xlink:to="loc_bxp_GatewayCommonsAndSevenSevenFiveZeroWisconsinAvenueMember_019edbbc-1ec9-7110-909e-a243c34ccba5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c84-af06-92884c6e4459" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019edbbc-1ec9-7c84-af06-92884c6e4459" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1ec9-76a9-9ebd-c80b9448e7f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1ec9-76a9-9ebd-c80b9448e7f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ContractualSalePrice_019edbbc-1ec9-708b-9024-228be5717181" xlink:href="bxp-20260630.xsd#bxp_ContractualSalePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_bxp_ContractualSalePrice_019edbbc-1ec9-708b-9024-228be5717181" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1ec9-79a4-8737-2316f295d7fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromSaleOfEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquityMethodInvestments_019edbbc-1ec9-79a4-8737-2316f295d7fe" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-72b9-95d3-a08cd5bcf2cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019edbbc-1ec9-72b9-95d3-a08cd5bcf2cf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1ec9-7485-8ac4-fa8b2fa530b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7028-bae5-eab608c56a89" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1ec9-7485-8ac4-fa8b2fa530b2" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/InvestmentinUnconsolidatedJointVenturesNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#InvestmentinUnconsolidatedJointVenturesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/InvestmentinUnconsolidatedJointVenturesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1ec9-7c64-9dc7-5ee728b81ebd" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPlazaMember_019fb977-68f9-7f21-945b-48c4fa3b7a74" xlink:href="bxp-20260630.xsd#bxp_SafecoPlazaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:to="loc_bxp_SafecoPlazaMember_019fb977-68f9-7f21-945b-48c4fa3b7a74" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FiveZeroZeroNorthCapitolMember_019fb977-f80b-7cce-84e6-3952fa15b6a1" xlink:href="bxp-20260630.xsd#bxp_FiveZeroZeroNorthCapitolMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:to="loc_bxp_FiveZeroZeroNorthCapitolMember_019fb977-f80b-7cce-84e6-3952fa15b6a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SkymarkMember_019fb978-d544-7cc9-b7f6-422a587a9b00" xlink:href="bxp-20260630.xsd#bxp_SkymarkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:to="loc_bxp_SkymarkMember_019fb978-d544-7cc9-b7f6-422a587a9b00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OneThreeOneFiveZeroWorldgateDriveMember_019fb9a9-ca57-7805-b44d-ba962fb8c29d" xlink:href="bxp-20260630.xsd#bxp_OneThreeOneFiveZeroWorldgateDriveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1ec9-7f45-893c-47b5f6217572" xlink:to="loc_bxp_OneThreeOneFiveZeroWorldgateDriveMember_019fb9a9-ca57-7805-b44d-ba962fb8c29d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7619-b534-abe4805b0d4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7619-b534-abe4805b0d4c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7619-b534-abe4805b0d4c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7619-b534-abe4805b0d4c" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7619-b534-abe4805b0d4c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7e71-a089-9ab8796c8eab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1ec9-7619-b534-abe4805b0d4c" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7e71-a089-9ab8796c8eab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-78e0-8a56-f64ef2a0b0ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1ec9-7e71-a089-9ab8796c8eab" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1ec9-78e0-8a56-f64ef2a0b0ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1ec9-7f59-9b8f-cb3a9407b456" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1ec9-7f59-9b8f-cb3a9407b456" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-7f59-9b8f-cb3a9407b456_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7f59-9b8f-cb3a9407b456" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-7f59-9b8f-cb3a9407b456_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1ec9-746b-ae37-acaa177183b9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1ec9-7f59-9b8f-cb3a9407b456" xlink:to="loc_dei_EntityDomain_019edbbc-1ec9-746b-ae37-acaa177183b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-78fa-891a-81162bbe0bae" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-746b-ae37-acaa177183b9" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-78fa-891a-81162bbe0bae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-744e-a985-beb29a6dfe22" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1ec9-746b-ae37-acaa177183b9" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1ec9-744e-a985-beb29a6dfe22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7fb8-9079-8f5ce8459907" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7fb8-9079-8f5ce8459907" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7fb8-9079-8f5ce8459907_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7fb8-9079-8f5ce8459907" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7fb8-9079-8f5ce8459907_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1ec9-7fb8-9079-8f5ce8459907" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PRIIBXPRestonGatewayLLCMember_019fb97e-a040-7435-8685-3227a2bbf6a4" xlink:href="bxp-20260630.xsd#bxp_PRIIBXPRestonGatewayLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:to="loc_bxp_PRIIBXPRestonGatewayLLCMember_019fb97e-a040-7435-8685-3227a2bbf6a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_WorldgateMultifamilyJVLLCMember_019fb9a7-cb98-7b19-a58a-9fae5c8638f1" xlink:href="bxp-20260630.xsd#bxp_WorldgateMultifamilyJVLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:to="loc_bxp_WorldgateMultifamilyJVLLCMember_019fb9a7-cb98-7b19-a58a-9fae5c8638f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FiveZeroZeroNorthCapitolLlcMember_019fc365-c673-7221-9e43-4b87dbc66e9e" xlink:href="bxp-20260630.xsd#bxp_FiveZeroZeroNorthCapitolLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:to="loc_bxp_FiveZeroZeroNorthCapitolLlcMember_019fc365-c673-7221-9e43-4b87dbc66e9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SafecoPlazaREITLLCMember_019fc36e-2787-7dd0-ace2-764b9cd2df74" xlink:href="bxp-20260630.xsd#bxp_SafecoPlazaREITLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1ec9-7007-ab71-c9a6db5f54ac" xlink:to="loc_bxp_SafecoPlazaREITLLCMember_019fc36e-2787-7dd0-ace2-764b9cd2df74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_srt_OwnershipAxis_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1ec9-7439-b70a-cf298b1d7e2f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1ec9-775e-a6cc-2c6dcfdee6ef" xlink:to="loc_srt_OwnershipDomain_019edbbc-1ec9-7439-b70a-cf298b1d7e2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-708a-8eb8-bbacf2b29f81" xlink:href="bxp-20260630.xsd#bxp_JointVenturePartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-7439-b70a-cf298b1d7e2f" xlink:to="loc_bxp_JointVenturePartnerMember_019edbbc-1ec9-708a-8eb8-bbacf2b29f81" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1ec9-73d5-ac56-30e1ee48ef0b" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1ec9-7439-b70a-cf298b1d7e2f" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1ec9-73d5-ac56-30e1ee48ef0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019edbbc-1ec9-7fd1-91fa-c178c47a2365" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_srt_RangeAxis_019edbbc-1ec9-7fd1-91fa-c178c47a2365" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1ec9-7fd1-91fa-c178c47a2365_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019edbbc-1ec9-7fd1-91fa-c178c47a2365" xlink:to="loc_srt_RangeMember_019edbbc-1ec9-7fd1-91fa-c178c47a2365_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1ec9-7c6a-b04f-7a9fb1bb72f9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019edbbc-1ec9-7fd1-91fa-c178c47a2365" xlink:to="loc_srt_RangeMember_019edbbc-1ec9-7c6a-b04f-7a9fb1bb72f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019edbbc-1ec9-7986-99a6-8c036fe94eb0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1ec9-7c6a-b04f-7a9fb1bb72f9" xlink:to="loc_srt_MaximumMember_019edbbc-1ec9-7986-99a6-8c036fe94eb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019edbbc-1ec9-7061-8445-6c2748f264b0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1ec9-7c6a-b04f-7a9fb1bb72f9" xlink:to="loc_srt_MinimumMember_019edbbc-1ec9-7061-8445-6c2748f264b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019fb94b-f069-77d1-8857-358199f73cad" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019fb94b-f069-77d1-8857-358199f73cad" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019fb94b-f069-77d1-8857-358199f73cad_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019fb94b-f069-77d1-8857-358199f73cad" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019fb94b-f069-77d1-8857-358199f73cad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019fb94b-f069-7049-b021-6ac35c413169" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019fb94b-f069-77d1-8857-358199f73cad" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019fb94b-f069-7049-b021-6ac35c413169" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ApartmentBuildingMember_019fb94c-14d5-738b-91f3-635e01008eed" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ApartmentBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019fb94b-f069-7049-b021-6ac35c413169" xlink:to="loc_srt_ApartmentBuildingMember_019fb94c-14d5-738b-91f3-635e01008eed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019fb97f-9b9c-781e-b408-51ce4b3f2fa6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019fb97f-9b9c-781e-b408-51ce4b3f2fa6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-781e-b408-51ce4b3f2fa6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb97f-9b9c-781e-b408-51ce4b3f2fa6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-781e-b408-51ce4b3f2fa6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-7301-817a-d9638163bbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb97f-9b9c-781e-b408-51ce4b3f2fa6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-7301-817a-d9638163bbe5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_019fb980-275c-7564-9c7e-c286e7613a06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-7301-817a-d9638163bbe5" xlink:to="loc_us-gaap_ConstructionLoansMember_019fb980-275c-7564-9c7e-c286e7613a06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesMember_019fb997-ed0d-7cbb-8af5-55274c472d1d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb97f-9b9c-7301-817a-d9638163bbe5" xlink:to="loc_us-gaap_MortgagesMember_019fb997-ed0d-7cbb-8af5-55274c472d1d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb991-6657-73ae-9d4d-94c2419ce67f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb991-6657-73ae-9d4d-94c2419ce67f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb991-6657-73ae-9d4d-94c2419ce67f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb991-6657-73ae-9d4d-94c2419ce67f" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb991-6657-73ae-9d4d-94c2419ce67f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fb991-6657-774c-8ca9-b2096787733e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fb991-6657-73ae-9d4d-94c2419ce67f" xlink:to="loc_us-gaap_RelatedPartyDomain_019fb991-6657-774c-8ca9-b2096787733e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019fb991-6657-74c3-ae27-5cf0ec41f10f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fb991-6657-774c-8ca9-b2096787733e" xlink:to="loc_us-gaap_RelatedPartyMember_019fb991-6657-74c3-ae27-5cf0ec41f10f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019fb9a2-8c71-7d5e-8232-aef6476d01ac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019fb9a2-8c71-7d5e-8232-aef6476d01ac" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fb9a2-8c71-7d5e-8232-aef6476d01ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fb9a2-8c71-7d5e-8232-aef6476d01ac" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fb9a2-8c71-7d5e-8232-aef6476d01ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019fb9a2-8c71-7893-88b9-8b65ba95fef1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019fb9a2-8c71-7d5e-8232-aef6476d01ac" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019fb9a2-8c71-7893-88b9-8b65ba95fef1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCapMember_019fb9a2-c75b-7292-9910-eb7e62b48a9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateCapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019fb9a2-8c71-7893-88b9-8b65ba95fef1" xlink:to="loc_us-gaap_InterestRateCapMember_019fb9a2-c75b-7292-9910-eb7e62b48a9f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019fc33a-9ea9-7aec-a757-ef79e34f1740" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_DebtInstrumentAxis_019fc33a-9ea9-7aec-a757-ef79e34f1740" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7aec-a757-ef79e34f1740_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fc33a-9ea9-7aec-a757-ef79e34f1740" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7aec-a757-ef79e34f1740_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7cea-804b-79fb6a6750a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019fc33a-9ea9-7aec-a757-ef79e34f1740" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7cea-804b-79fb6a6750a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoteBMember_019fc33b-4dc2-7cfb-8810-de5e63de1fef" xlink:href="bxp-20260630.xsd#bxp_NoteBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7cea-804b-79fb6a6750a2" xlink:to="loc_bxp_NoteBMember_019fc33b-4dc2-7cfb-8810-de5e63de1fef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoteAMember_019fc33e-8589-7959-a706-4ebdf9ee8825" xlink:href="bxp-20260630.xsd#bxp_NoteAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019fc33a-9ea9-7cea-804b-79fb6a6750a2" xlink:to="loc_bxp_NoteAMember_019fc33e-8589-7959-a706-4ebdf9ee8825" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationAxis_019fc342-605d-7e99-b840-172f94abcd8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoanRestructuringModificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019edbbc-1ec9-7d8a-bf27-7a36bb0f28cf" xlink:to="loc_us-gaap_LoanRestructuringModificationAxis_019fc342-605d-7e99-b840-172f94abcd8c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019fc342-605d-7e99-b840-172f94abcd8c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019fc342-605d-7e99-b840-172f94abcd8c" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019fc342-605d-7e99-b840-172f94abcd8c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoanRestructuringModificationDomain_019fc342-605d-7845-b205-e6f6d790b801" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoanRestructuringModificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LoanRestructuringModificationAxis_019fc342-605d-7e99-b840-172f94abcd8c" xlink:to="loc_us-gaap_LoanRestructuringModificationDomain_019fc342-605d-7845-b205-e6f6d790b801" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExtendedMaturityMember_019fc342-ddf9-7e10-a348-1a86695993d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExtendedMaturityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LoanRestructuringModificationDomain_019fc342-605d-7845-b205-e6f6d790b801" xlink:to="loc_us-gaap_ExtendedMaturityMember_019fc342-ddf9-7e10-a348-1a86695993d8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019fb936-63ce-7898-b0b6-56b2a4edd31b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019fb936-63ce-7898-b0b6-56b2a4edd31b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019fb937-e7d9-766e-a236-867d18a91bd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_NetRentableArea_019fb937-e7d9-766e-a236-867d18a91bd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fb93d-448a-7e7e-9160-ed1ee40aa2b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019fb93d-448a-7e7e-9160-ed1ee40aa2b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb947-0f3e-7dc5-9757-3811b4835c95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb947-0f3e-7dc5-9757-3811b4835c95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ExtensionOptioninyears_019fb949-1faf-7b5f-a424-0d561834e925" xlink:href="bxp-20260630.xsd#bxp_ExtensionOptioninyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_bxp_ExtensionOptioninyears_019fb949-1faf-7b5f-a424-0d561834e925" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019fb94a-d47d-7d7f-bb15-e221cdff61fe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfUnitsInRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019fb94a-d47d-7d7f-bb15-e221cdff61fe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019fb94f-ad37-7f85-802b-10e1d2506695" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019fb94f-ad37-7f85-802b-10e1d2506695" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019fb950-3da9-78bf-be9a-9197b8bdfa01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019fb950-3da9-78bf-be9a-9197b8bdfa01" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeCapInterestRate_019fb976-9e07-709e-b5cb-acb46ac8473a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeCapInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DerivativeCapInterestRate_019fb976-9e07-709e-b5cb-acb46ac8473a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NumberOfExtensionOptions_019fb985-68be-7e1d-b7c2-c492ec719991" xlink:href="bxp-20260630.xsd#bxp_NumberOfExtensionOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_bxp_NumberOfExtensionOptions_019fb985-68be-7e1d-b7c2-c492ec719991" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_019fb991-6657-7981-bcf1-16c2d8f91175" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_NotesReceivableNet_019fb991-6657-7981-bcf1-16c2d8f91175" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019fb99a-b5c9-73d3-bea1-6d9686288a01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019fb99a-b5c9-73d3-bea1-6d9686288a01" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019fb9a7-4142-70ce-a247-c344bc8327bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_019fb9a7-4142-70ce-a247-c344bc8327bc" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturityDate_019fc337-e496-7ca1-876e-725ae974f18c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_LongTermDebtMaturityDate_019fc337-e496-7ca1-876e-725ae974f18c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019fc878-5f86-7cd7-9d5f-5196f05dfeb3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetAcquisitionConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferred_019fc878-5f86-7cd7-9d5f-5196f05dfeb3" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionConsiderationTransferredOtherAssets_019fc87a-7681-7101-9948-f7717f406af9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetAcquisitionConsiderationTransferredOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019edbbc-1ec9-7959-9194-f2488618b005" xlink:to="loc_us-gaap_AssetAcquisitionConsiderationTransferredOtherAssets_019fc87a-7681-7101-9948-f7717f406af9" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ScheduleofUnsecuredSeniorNotesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#ScheduleofUnsecuredSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ScheduleofUnsecuredSeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-7d0f-a8fb-1480d8cd48dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-7d0f-a8fb-1480d8cd48dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1eca-70df-83f7-23b09ccc36c0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-7d0f-a8fb-1480d8cd48dd" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1eca-70df-83f7-23b09ccc36c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-70df-83f7-23b09ccc36c0_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-70df-83f7-23b09ccc36c0" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-70df-83f7-23b09ccc36c0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-7e43-948a-08a95b64eb42" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-70df-83f7-23b09ccc36c0" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-7e43-948a-08a95b64eb42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-771c-a35b-90551922414d" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1eca-7e43-948a-08a95b64eb42" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-771c-a35b-90551922414d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7dfb-b2cd-5998f81184d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-7d0f-a8fb-1480d8cd48dd" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7dfb-b2cd-5998f81184d6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7dfb-b2cd-5998f81184d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7dfb-b2cd-5998f81184d6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7dfb-b2cd-5998f81184d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7671-8276-39c9767833a5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7dfb-b2cd-5998f81184d6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7671-8276-39c9767833a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019edbbc-1eca-73e6-85fc-8137c60e4f3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7671-8276-39c9767833a5" xlink:to="loc_us-gaap_SeniorNotesMember_019edbbc-1eca-73e6-85fc-8137c60e4f3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7910-9a79-1a7ddf0a8902" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-7d0f-a8fb-1480d8cd48dd" xlink:to="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7910-9a79-1a7ddf0a8902" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7910-9a79-1a7ddf0a8902_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7910-9a79-1a7ddf0a8902" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7910-9a79-1a7ddf0a8902_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7910-9a79-1a7ddf0a8902" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreePointFourNineFivePercentUnsecuredSeniorNotesMember_019edbbc-1eca-7dd7-bc3f-ff3a823afd6e" xlink:href="bxp-20260630.xsd#bxp_ThreePointFourNineFivePercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_ThreePointFourNineFivePercentUnsecuredSeniorNotesMember_019edbbc-1eca-7dd7-bc3f-ff3a823afd6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SixPointNineTwoFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7d66-be33-92c10a1cdaef" xlink:href="bxp-20260630.xsd#bxp_SixPointNineTwoFourPercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_SixPointNineTwoFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7d66-be33-92c10a1cdaef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FourPointSixTwoEightPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7246-93b5-a1182f02dc2d" xlink:href="bxp-20260630.xsd#bxp_FourPointSixTwoEightPercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_FourPointSixTwoEightPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7246-93b5-a1182f02dc2d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreePointFiveZeroFivePercentUnsecuredSeniorNotesMember_019edbbc-1eca-722d-aacd-5418be6a378f" xlink:href="bxp-20260630.xsd#bxp_ThreePointFiveZeroFivePercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_ThreePointFiveZeroFivePercentUnsecuredSeniorNotesMember_019edbbc-1eca-722d-aacd-5418be6a378f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoPointNineEightFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7050-a990-ad2414fcde1f" xlink:href="bxp-20260630.xsd#bxp_TwoPointNineEightFourPercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_TwoPointNineEightFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-7050-a990-ad2414fcde1f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreepointthreefourthreepercentunsecuredseniornotesMember_019edbbc-1eca-75d4-8870-4f97cd92068c" xlink:href="bxp-20260630.xsd#bxp_ThreepointthreefourthreepercentunsecuredseniornotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_ThreepointthreefourthreepercentunsecuredseniornotesMember_019edbbc-1eca-75d4-8870-4f97cd92068c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoPointSixSevenOnePercentUnsecuredSeniorNotesMember_019edbbc-1eca-759d-b6c1-37e61a8d4643" xlink:href="bxp-20260630.xsd#bxp_TwoPointSixSevenOnePercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_TwoPointSixSevenOnePercentUnsecuredSeniorNotesMember_019edbbc-1eca-759d-b6c1-37e61a8d4643" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoPointFiveTwoFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-73cd-8299-500de73d4a91" xlink:href="bxp-20260630.xsd#bxp_TwoPointFiveTwoFourPercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_TwoPointFiveTwoFourPercentUnsecuredSeniorNotesMember_019edbbc-1eca-73cd-8299-500de73d4a91" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SixPointSixOneNinePercentMember_019edbbc-1eca-7644-99fa-cddde3da8544" xlink:href="bxp-20260630.xsd#bxp_SixPointSixOneNinePercentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_SixPointSixOneNinePercentMember_019edbbc-1eca-7644-99fa-cddde3da8544" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_FivePointEightFourTwoPercentMember_019edbbc-1eca-7f69-ab79-5db6a4b2018b" xlink:href="bxp-20260630.xsd#bxp_FivePointEightFourTwoPercentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7004-a45c-6dffd6255799" xlink:to="loc_bxp_FivePointEightFourTwoPercentMember_019edbbc-1eca-7f69-ab79-5db6a4b2018b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-7ce2-b866-ab8dd90512ea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-7ce2-b866-ab8dd90512ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019edbbc-1eca-773b-bfbc-c635a0449933" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019edbbc-1eca-773b-bfbc-c635a0449933" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1eca-76b8-9f2e-371871d5f04d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1eca-76b8-9f2e-371871d5f04d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturityDate_019edbbc-1eca-73bc-9b04-f621765d9794" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_LongTermDebtMaturityDate_019edbbc-1eca-73bc-9b04-f621765d9794" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019edbbc-1eca-7eaf-8f52-2b8dd922f00d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscount_019edbbc-1eca-7eaf-8f52-2b8dd922f00d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_019edbbc-1eca-731a-a35e-271888b77242" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_019edbbc-1eca-731a-a35e-271888b77242" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotes_019edbbc-1eca-78e2-bfbb-9e9b1ca5ad06" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-7ab0-bc5b-3a42d1359edc" xlink:to="loc_us-gaap_SeniorNotes_019edbbc-1eca-78e2-bfbb-9e9b1ca5ad06" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/UnsecuredSeniorNotesNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#UnsecuredSeniorNotesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/UnsecuredSeniorNotesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-74d3-9a90-873a850ac8c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-782a-8700-6c1bef97b603" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-74d3-9a90-873a850ac8c8" xlink:to="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-782a-8700-6c1bef97b603" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7463-bcbd-81cfb2d47d44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-782a-8700-6c1bef97b603" xlink:to="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7463-bcbd-81cfb2d47d44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7463-bcbd-81cfb2d47d44_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7463-bcbd-81cfb2d47d44" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-7463-bcbd-81cfb2d47d44_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-79a4-bdf2-adb72e88d985" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019edbbc-1eca-7463-bcbd-81cfb2d47d44" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-79a4-bdf2-adb72e88d985" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreePointSevenSixSixPercentUnsecuredSeniorNotesMember_019edbbc-1eca-773b-a079-e971267d149a" xlink:href="bxp-20260630.xsd#bxp_ThreePointSevenSixSixPercentUnsecuredSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019edbbc-1eca-79a4-bdf2-adb72e88d985" xlink:to="loc_bxp_ThreePointSevenSixSixPercentUnsecuredSeniorNotesMember_019edbbc-1eca-773b-a079-e971267d149a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7b18-a73d-4175a141f87a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-782a-8700-6c1bef97b603" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7b18-a73d-4175a141f87a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7b18-a73d-4175a141f87a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7b18-a73d-4175a141f87a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7b18-a73d-4175a141f87a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7270-b717-db0cd7d9cf72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019edbbc-1eca-7b18-a73d-4175a141f87a" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7270-b717-db0cd7d9cf72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019edbbc-1eca-7394-8ecd-cc460aee76c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019edbbc-1eca-7270-b717-db0cd7d9cf72" xlink:to="loc_us-gaap_SeniorNotesMember_019edbbc-1eca-7394-8ecd-cc460aee76c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1eca-7868-aec3-c2b11fc33ce2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019edbbc-1eca-782a-8700-6c1bef97b603" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1eca-7868-aec3-c2b11fc33ce2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-7868-aec3-c2b11fc33ce2_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-7868-aec3-c2b11fc33ce2" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-7868-aec3-c2b11fc33ce2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-757d-ba19-53f9789f213e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-7868-aec3-c2b11fc33ce2" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-757d-ba19-53f9789f213e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-7afb-9a6c-8b86fc3a75f4" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1eca-757d-ba19-53f9789f213e" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-7afb-9a6c-8b86fc3a75f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1eca-7810-8b71-5732477fa2e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-74d3-9a90-873a850ac8c8" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019edbbc-1eca-7810-8b71-5732477fa2e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-7e33-b660-25d2514d8716" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019edbbc-1eca-74d3-9a90-873a850ac8c8" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-7e33-b660-25d2514d8716" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/DerivativeInstrumentsandHedgingActivitiesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#DerivativeInstrumentsandHedgingActivitiesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/DerivativeInstrumentsandHedgingActivitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_019edbbc-1eca-72d1-927d-5d2e75fcc77d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_DerivativeTable_019edbbc-1eca-72d1-927d-5d2e75fcc77d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1eca-758c-9c3c-5e9e7aebdd87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019edbbc-1eca-72d1-927d-5d2e75fcc77d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1eca-758c-9c3c-5e9e7aebdd87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1eca-758c-9c3c-5e9e7aebdd87_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1eca-758c-9c3c-5e9e7aebdd87" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1eca-758c-9c3c-5e9e7aebdd87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1eca-7d81-9c28-fa0775069dda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019edbbc-1eca-758c-9c3c-5e9e7aebdd87" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1eca-7d81-9c28-fa0775069dda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019edbbc-1eca-71cf-8160-1d81459c1cd0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019edbbc-1eca-7d81-9c28-fa0775069dda" xlink:to="loc_us-gaap_InterestRateSwapMember_019edbbc-1eca-71cf-8160-1d81459c1cd0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019edbbc-1eca-70a9-bc80-95e4cd74667b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_019edbbc-1eca-72d1-927d-5d2e75fcc77d" xlink:to="loc_srt_RangeAxis_019edbbc-1eca-70a9-bc80-95e4cd74667b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1eca-70a9-bc80-95e4cd74667b_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019edbbc-1eca-70a9-bc80-95e4cd74667b" xlink:to="loc_srt_RangeMember_019edbbc-1eca-70a9-bc80-95e4cd74667b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1eca-7bc9-bbd0-3f03e8963adb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019edbbc-1eca-70a9-bc80-95e4cd74667b" xlink:to="loc_srt_RangeMember_019edbbc-1eca-7bc9-bbd0-3f03e8963adb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019edbbc-1eca-7e07-b675-1cb8f70067d2" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1eca-7bc9-bbd0-3f03e8963adb" xlink:to="loc_srt_MinimumMember_019edbbc-1eca-7e07-b675-1cb8f70067d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019edbbc-1eca-70d1-a34a-12774fe318d3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1eca-7bc9-bbd0-3f03e8963adb" xlink:to="loc_srt_MaximumMember_019edbbc-1eca-70d1-a34a-12774fe318d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeSwapType_019edbbc-1eca-7f63-af1d-b316a2f0d623" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeSwapType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_DerivativeSwapType_019edbbc-1eca-7f63-af1d-b316a2f0d623" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019edbbc-1eca-7d6a-8f85-b52a4793bf1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019edbbc-1eca-7d6a-8f85-b52a4793bf1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeMaturityDates_019edbbc-1eca-743d-a120-1b0d56bfb7d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeMaturityDates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_DerivativeMaturityDates_019edbbc-1eca-743d-a120-1b0d56bfb7d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_019edbbc-1eca-7493-a757-3da0c622e29e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_019edbbc-1eca-7493-a757-3da0c622e29e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue_019edbbc-1eca-7bf0-97b6-12fa7a66d2ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_019edbbc-1eca-7c88-9153-73de9ed73c62" xlink:to="loc_us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue_019edbbc-1eca-7bf0-97b6-12fa7a66d2ad" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/DerivativeInstrumentsandHedgingActivitiesGainLossDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#DerivativeInstrumentsandHedgingActivitiesGainLossDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/DerivativeInstrumentsandHedgingActivitiesGainLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019edbbc-1eca-79ec-afc7-98524ea92049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019edbbc-1eca-7939-b463-12e9af97468f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019edbbc-1eca-79ec-afc7-98524ea92049" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019edbbc-1eca-7939-b463-12e9af97468f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019edbbc-1eca-7d91-9367-c7363743aa21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityRecurringBasisStillHeldUnrealizedGainLossOci"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019edbbc-1eca-79ec-afc7-98524ea92049" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityRecurringBasisStillHeldUnrealizedGainLossOci_019edbbc-1eca-7d91-9367-c7363743aa21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_019edbbc-1eca-7b3f-a721-a887a2f9efce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019edbbc-1eca-79ec-afc7-98524ea92049" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_019edbbc-1eca-7b3f-a721-a887a2f9efce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossFromComponentsExcludedFromAssessmentOfCashFlowHedgeEffectivenessNet_019edbbc-1eca-7e1b-bdf8-5a0690fca94f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossFromComponentsExcludedFromAssessmentOfCashFlowHedgeEffectivenessNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019edbbc-1eca-79ec-afc7-98524ea92049" xlink:to="loc_us-gaap_GainLossFromComponentsExcludedFromAssessmentOfCashFlowHedgeEffectivenessNet_019edbbc-1eca-7e1b-bdf8-5a0690fca94f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/CommitmentsAndContingenciesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#CommitmentsAndContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:href="bxp-20260630.xsd#bxp_CommitmentsAndContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:href="bxp-20260630.xsd#bxp_CommitmentsAndContingenciesDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1eca-7ee1-a77f-9923ac2f83b0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1eca-7ee1-a77f-9923ac2f83b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1eca-7ee1-a77f-9923ac2f83b0_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1eca-7ee1-a77f-9923ac2f83b0" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1eca-7ee1-a77f-9923ac2f83b0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1eca-7bac-abcf-6d530bccbcb8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MortgageLoansOnRealEstateNamePropertyTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis_019edbbc-1eca-7ee1-a77f-9923ac2f83b0" xlink:to="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1eca-7bac-abcf-6d530bccbcb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OfficeBuildingMember_019edbbc-1eca-765c-9a6f-6df2fd083f9a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OfficeBuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_MortgageLoansOnRealEstateNamePropertyTypeDomain_019edbbc-1eca-7bac-abcf-6d530bccbcb8" xlink:to="loc_srt_OfficeBuildingMember_019edbbc-1eca-765c-9a6f-6df2fd083f9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1eca-7c36-863f-119a48b918ae" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1eca-7c36-863f-119a48b918ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-7c36-863f-119a48b918ae_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1eca-7c36-863f-119a48b918ae" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-7c36-863f-119a48b918ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1eca-7c36-863f-119a48b918ae" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MetropolitanSquareMember_019edbbc-1eca-7ca5-93e2-c706614f0282" xlink:href="bxp-20260630.xsd#bxp_MetropolitanSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:to="loc_bxp_MetropolitanSquareMember_019edbbc-1eca-7ca5-93e2-c706614f0282" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoNineZeroBinneyMember_019edbbc-1eca-73af-a3df-2e5dc1724d09" xlink:href="bxp-20260630.xsd#bxp_TwoNineZeroBinneyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:to="loc_bxp_TwoNineZeroBinneyMember_019edbbc-1eca-73af-a3df-2e5dc1724d09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_TwoFiveZeroBinneyStreetMember_019edbbc-1eca-7f0f-ab3d-2f44625b0e29" xlink:href="bxp-20260630.xsd#bxp_TwoFiveZeroBinneyStreetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:to="loc_bxp_TwoFiveZeroBinneyStreetMember_019edbbc-1eca-7f0f-ab3d-2f44625b0e29" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SixZeroOneLexingtonAvenueMember_019edbbc-1eca-74b9-98a5-9d9e4e56c487" xlink:href="bxp-20260630.xsd#bxp_SixZeroOneLexingtonAvenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:to="loc_bxp_SixZeroOneLexingtonAvenueMember_019edbbc-1eca-74b9-98a5-9d9e4e56c487" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeHudsonBoulevardMember_019edbbc-1eca-7bcb-b11d-f75dcd338794" xlink:href="bxp-20260630.xsd#bxp_ThreeHudsonBoulevardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1eca-71b2-9e4b-31cd7f229ce5" xlink:to="loc_bxp_ThreeHudsonBoulevardMember_019edbbc-1eca-7bcb-b11d-f75dcd338794" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1eca-7857-9aae-c9629f029cff" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1eca-7857-9aae-c9629f029cff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-7857-9aae-c9629f029cff_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1eca-7857-9aae-c9629f029cff" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-7857-9aae-c9629f029cff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-713f-8c10-e3e0e4ed981c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019edbbc-1eca-7857-9aae-c9629f029cff" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-713f-8c10-e3e0e4ed981c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SevenSixSevenVentureLlcMember_019edbbc-1eca-75a5-b338-d63181ed49f4" xlink:href="bxp-20260630.xsd#bxp_SevenSixSevenVentureLlcMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-713f-8c10-e3e0e4ed981c" xlink:to="loc_bxp_SevenSixSevenVentureLlcMember_019edbbc-1eca-75a5-b338-d63181ed49f4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MetropolitanSquareMember_019edbbc-1eca-719e-8102-034a90876032" xlink:href="bxp-20260630.xsd#bxp_MetropolitanSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-713f-8c10-e3e0e4ed981c" xlink:to="loc_bxp_MetropolitanSquareMember_019edbbc-1eca-719e-8102-034a90876032" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeHudsonBoulevardMember_019edbbc-1eca-7d32-a6ff-62c2f3aab2b3" xlink:href="bxp-20260630.xsd#bxp_ThreeHudsonBoulevardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019edbbc-1eca-713f-8c10-e3e0e4ed981c" xlink:to="loc_bxp_ThreeHudsonBoulevardMember_019edbbc-1eca-7d32-a6ff-62c2f3aab2b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1eca-75dc-afdb-6b70d2b95655" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1eca-75dc-afdb-6b70d2b95655" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-75dc-afdb-6b70d2b95655_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-75dc-afdb-6b70d2b95655" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-75dc-afdb-6b70d2b95655_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1eca-7581-9d41-b216d9985fa0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1eca-75dc-afdb-6b70d2b95655" xlink:to="loc_dei_EntityDomain_019edbbc-1eca-7581-9d41-b216d9985fa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-71b7-9ee0-a3ba4a15657b" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1eca-7581-9d41-b216d9985fa0" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1eca-71b7-9ee0-a3ba4a15657b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019edbbc-1eca-7eef-82fd-d9eeafa149fa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_srt_StatementScenarioAxis_019edbbc-1eca-7eef-82fd-d9eeafa149fa" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019edbbc-1eca-7eef-82fd-d9eeafa149fa_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019edbbc-1eca-7eef-82fd-d9eeafa149fa" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019edbbc-1eca-7eef-82fd-d9eeafa149fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019edbbc-1eca-7377-908d-77abd9bcc22c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019edbbc-1eca-7eef-82fd-d9eeafa149fa" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019edbbc-1eca-7377-908d-77abd9bcc22c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScenarioPlanMember_019edbbc-1eca-77fa-93bc-f0cfb65ca8b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScenarioPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019edbbc-1eca-7377-908d-77abd9bcc22c" xlink:to="loc_us-gaap_ScenarioPlanMember_019edbbc-1eca-77fa-93bc-f0cfb65ca8b4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019edbbc-1eca-788b-a9c6-bfc4a00aceef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019edbbc-1eca-788b-a9c6-bfc4a00aceef" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019edbbc-1eca-788b-a9c6-bfc4a00aceef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019edbbc-1eca-788b-a9c6-bfc4a00aceef" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019edbbc-1eca-788b-a9c6-bfc4a00aceef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019edbbc-1eca-735e-8390-0455b3e33515" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019edbbc-1eca-788b-a9c6-bfc4a00aceef" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019edbbc-1eca-735e-8390-0455b3e33515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_019edbbc-1eca-733c-a914-e51e5402c3c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_InvestmentTypeAxis_019edbbc-1eca-733c-a914-e51e5402c3c8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1eca-733c-a914-e51e5402c3c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_019edbbc-1eca-733c-a914-e51e5402c3c8" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1eca-733c-a914-e51e5402c3c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1eca-75c3-a27e-f51d427f6bfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_019edbbc-1eca-733c-a914-e51e5402c3c8" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1eca-75c3-a27e-f51d427f6bfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubordinatedDebtMember_019edbbc-1eca-7cb0-af70-fb4d0116dc6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubordinatedDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_019edbbc-1eca-75c3-a27e-f51d427f6bfe" xlink:to="loc_us-gaap_SubordinatedDebtMember_019edbbc-1eca-7cb0-af70-fb4d0116dc6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1eca-7201-8063-fbf1ecd22a80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1eca-7201-8063-fbf1ecd22a80" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1eca-7201-8063-fbf1ecd22a80_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1eca-7201-8063-fbf1ecd22a80" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1eca-7201-8063-fbf1ecd22a80_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019edbbc-1eca-7b41-b1be-3f3b2bb152eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019edbbc-1eca-7201-8063-fbf1ecd22a80" xlink:to="loc_us-gaap_RelatedPartyDomain_019edbbc-1eca-7b41-b1be-3f3b2bb152eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_019edbbc-1eca-7cbc-a09c-fa42c0b1ef7a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019edbbc-1eca-7b41-b1be-3f3b2bb152eb" xlink:to="loc_srt_AffiliatedEntityMember_019edbbc-1eca-7cbc-a09c-fa42c0b1ef7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019edbbc-1eca-7b30-afa4-1e461d7d039f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019edbbc-1eca-7b30-afa4-1e461d7d039f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_019edbbc-1eca-7b30-afa4-1e461d7d039f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019edbbc-1eca-7b30-afa4-1e461d7d039f" xlink:to="loc_us-gaap_ReceivableTypeDomain_019edbbc-1eca-7b30-afa4-1e461d7d039f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_019edbbc-1eca-7ceb-bd6a-b414154a4766" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_019edbbc-1eca-7b30-afa4-1e461d7d039f" xlink:to="loc_us-gaap_ReceivableTypeDomain_019edbbc-1eca-7ceb-bd6a-b414154a4766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableMember_019edbbc-1eca-7bab-9a99-dc16100c5d48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_019edbbc-1eca-7ceb-bd6a-b414154a4766" xlink:to="loc_us-gaap_NotesReceivableMember_019edbbc-1eca-7bab-9a99-dc16100c5d48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1eca-71d2-abf5-f529661470ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1eca-71d2-abf5-f529661470ad" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1eca-71d2-abf5-f529661470ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1eca-71d2-abf5-f529661470ad" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1eca-71d2-abf5-f529661470ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1eca-74d7-94d5-4429eb5900d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019edbbc-1eca-71d2-abf5-f529661470ad" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1eca-74d7-94d5-4429eb5900d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1eca-7276-b7e0-51ea793d5891" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019edbbc-1eca-74d7-94d5-4429eb5900d8" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019edbbc-1eca-7276-b7e0-51ea793d5891" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019edbbc-1eca-7220-82e8-2da40ebb2af0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019edbbc-1eca-7220-82e8-2da40ebb2af0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019edbbc-1eca-7220-82e8-2da40ebb2af0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019edbbc-1eca-7220-82e8-2da40ebb2af0" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019edbbc-1eca-7220-82e8-2da40ebb2af0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019edbbc-1eca-7613-8343-544a9bada792" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019edbbc-1eca-7220-82e8-2da40ebb2af0" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019edbbc-1eca-7613-8343-544a9bada792" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019edbbc-1eca-7314-a64e-f383432d6b2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019edbbc-1eca-7613-8343-544a9bada792" xlink:to="loc_us-gaap_RelatedPartyMember_019edbbc-1eca-7314-a64e-f383432d6b2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1eca-756a-a94c-3961e0cdaf8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_bxp_CommitmentsAndContingenciesDisclosureTable_019edbbc-1eca-7554-88e6-8a8f9f067ddb" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1eca-756a-a94c-3961e0cdaf8f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1eca-756a-a94c-3961e0cdaf8f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1eca-756a-a94c-3961e0cdaf8f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1eca-756a-a94c-3961e0cdaf8f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1eca-7eda-8071-3b8513c33381" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019edbbc-1eca-756a-a94c-3961e0cdaf8f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1eca-7eda-8071-3b8513c33381" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_019edbbc-1eca-7479-a0bc-c98b6bf35ad6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019edbbc-1eca-7eda-8071-3b8513c33381" xlink:to="loc_us-gaap_ConstructionInProgressMember_019edbbc-1eca-7479-a0bc-c98b6bf35ad6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LetterOfCreditAndPerformanceObligation_019edbbc-1eca-7057-9ca6-4f2d7b3f8e06" xlink:href="bxp-20260630.xsd#bxp_LetterOfCreditAndPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_LetterOfCreditAndPerformanceObligation_019edbbc-1eca-7057-9ca6-4f2d7b3f8e06" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1eca-7e94-8166-dcda902cfc2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1eca-7e94-8166-dcda902cfc2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCommitment_019edbbc-1eca-7e8a-ac5f-c22af40b0ad3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCommitment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_OtherCommitment_019edbbc-1eca-7e8a-ac5f-c22af40b0ad3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019edbbc-1eca-7acb-951a-e166963de714" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019edbbc-1eca-7acb-951a-e166963de714" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-792e-a9a4-621bfdcafffd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019edbbc-1eca-792e-a9a4-621bfdcafffd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableGross_019edbbc-1eca-7904-9cd9-1a2860ab6cb1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_NotesReceivableGross_019edbbc-1eca-7904-9cd9-1a2860ab6cb1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesReceivableNet_019edbbc-1eca-7e6a-9340-4b75a0df22d8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_NotesReceivableNet_019edbbc-1eca-7e6a-9340-4b75a0df22d8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019edbbc-1eca-73db-9508-51c6d7ab0d9c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019edbbc-1eca-73db-9508-51c6d7ab0d9c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesForGuaranteesOnLongDurationContractsGuaranteedBenefitLiabilityGross_019edbbc-1eca-7044-a301-5dbce9ffd4b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesForGuaranteesOnLongDurationContractsGuaranteedBenefitLiabilityGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_LiabilitiesForGuaranteesOnLongDurationContractsGuaranteedBenefitLiabilityGross_019edbbc-1eca-7044-a301-5dbce9ffd4b9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1eca-7450-b293-692780ec7243" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccruedLiabilitiesCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrentAndNoncurrent_019edbbc-1eca-7450-b293-692780ec7243" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForLegalSettlements_019edbbc-1eca-7116-9d36-478e8274f953" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsForLegalSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_PaymentsForLegalSettlements_019edbbc-1eca-7116-9d36-478e8274f953" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EstimatedLiabilityNotAccrued_019edbbc-1eca-7437-a3b6-41ca2080437a" xlink:href="bxp-20260630.xsd#bxp_EstimatedLiabilityNotAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_EstimatedLiabilityNotAccrued_019edbbc-1eca-7437-a3b6-41ca2080437a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyRangeOfPossibleLossPortionNotAccrued_019edbbc-1fab-7141-b64a-f928444e3059" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyRangeOfPossibleLossPortionNotAccrued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_LossContingencyRangeOfPossibleLossPortionNotAccrued_019edbbc-1fab-7141-b64a-f928444e3059" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ConsolidatedEntitiesOwnershipPercentage_019edbbc-1fab-7669-9fa1-04e1df539595" xlink:href="bxp-20260630.xsd#bxp_ConsolidatedEntitiesOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_ConsolidatedEntitiesOwnershipPercentage_019edbbc-1fab-7669-9fa1-04e1df539595" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Leasedpercentage_019edbbc-1fab-7825-b055-606038cbbe5c" xlink:href="bxp-20260630.xsd#bxp_Leasedpercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_Leasedpercentage_019edbbc-1fab-7825-b055-606038cbbe5c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNumberOfDefendants_019edbbc-1fab-759f-a00a-c002f21b50b9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNumberOfDefendants"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_us-gaap_LossContingencyNumberOfDefendants_019edbbc-1fab-759f-a00a-c002f21b50b9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_InsurancePolicyLimit_019edbbc-1fab-7879-977f-91e71fc6c028" xlink:href="bxp-20260630.xsd#bxp_InsurancePolicyLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_InsurancePolicyLimit_019edbbc-1fab-7879-977f-91e71fc6c028" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CoverageForActsOfTerrorismUnderTriaCoveredInExcessOfAmountCoveredByIxp_019edbbc-1fab-7f6a-9c3b-51a4286e38d7" xlink:href="bxp-20260630.xsd#bxp_CoverageForActsOfTerrorismUnderTriaCoveredInExcessOfAmountCoveredByIxp"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_CoverageForActsOfTerrorismUnderTriaCoveredInExcessOfAmountCoveredByIxp_019edbbc-1fab-7f6a-9c3b-51a4286e38d7" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPPropertyAndTerrorism_019edbbc-1fab-7d56-8102-3b09c40059e8" xlink:href="bxp-20260630.xsd#bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPPropertyAndTerrorism"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPPropertyAndTerrorism_019edbbc-1fab-7d56-8102-3b09c40059e8" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPTerrorism_019edbbc-1fab-71db-9561-d48992ddc1b0" xlink:href="bxp-20260630.xsd#bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPTerrorism"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_CoverageForActsOfTerrorismUnderTRIACoveredInExcessOfAmountCoveredByIXPTerrorism_019edbbc-1fab-71db-9561-d48992ddc1b0" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumOfCoverageCoveredByIXPAndExcessCoverageForPropertyAndTerrorism_019edbbc-1fab-7c65-90fd-96d3314cefea" xlink:href="bxp-20260630.xsd#bxp_SumOfCoverageCoveredByIXPAndExcessCoverageForPropertyAndTerrorism"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_SumOfCoverageCoveredByIXPAndExcessCoverageForPropertyAndTerrorism_019edbbc-1fab-7c65-90fd-96d3314cefea" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PerOccurrenceLimitForNbcrCoverage_019edbbc-1fab-7ed8-8851-539c7d0a33a6" xlink:href="bxp-20260630.xsd#bxp_PerOccurrenceLimitForNbcrCoverage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_PerOccurrenceLimitForNbcrCoverage_019edbbc-1fab-7ed8-8851-539c7d0a33a6" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ProgramTriggerValue_019edbbc-1fab-71df-9d87-15d32f2d7a18" xlink:href="bxp-20260630.xsd#bxp_ProgramTriggerValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_ProgramTriggerValue_019edbbc-1fab-71df-9d87-15d32f2d7a18" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ProgramTriggerCoinsurance_019edbbc-1fab-7e74-8f03-d4cea03cc10a" xlink:href="bxp-20260630.xsd#bxp_ProgramTriggerCoinsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_ProgramTriggerCoinsurance_019edbbc-1fab-7e74-8f03-d4cea03cc10a" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Programtriggerdeductible_019edbbc-1fab-7199-a257-4538e926b771" xlink:href="bxp-20260630.xsd#bxp_Programtriggerdeductible"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_Programtriggerdeductible_019edbbc-1fab-7199-a257-4538e926b771" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles_019edbbc-1fab-7f6c-9a63-4513870d167a" xlink:href="bxp-20260630.xsd#bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_PerOccurrenceLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles_019edbbc-1fab-7f6c-9a63-4513870d167a" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles_019edbbc-1fab-7b28-b7dd-4ecf17d53611" xlink:href="bxp-20260630.xsd#bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_AnnualAggregateLimitOfEarthQuakeInsuranceSanFranciscoandLosAngeles_019edbbc-1fab-7b28-b7dd-4ecf17d53611" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AmountOfEarthquakeInsuranceProvidedByIXPLLCAsDirectInsurerSanFranciscoandLosAngeles_019edbbc-1fab-7c28-ace3-326ab4080d99" xlink:href="bxp-20260630.xsd#bxp_AmountOfEarthquakeInsuranceProvidedByIXPLLCAsDirectInsurerSanFranciscoandLosAngeles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_AmountOfEarthquakeInsuranceProvidedByIXPLLCAsDirectInsurerSanFranciscoandLosAngeles_019edbbc-1fab-7c28-ace3-326ab4080d99" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySanFranciscoandLosAngeles_019edbbc-1fab-76e3-8e9e-c2c15e9877be" xlink:href="bxp-20260630.xsd#bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySanFranciscoandLosAngeles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySanFranciscoandLosAngeles_019edbbc-1fab-76e3-8e9e-c2c15e9877be" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PerOccurrenceLimitOfEarthquakeInsuranceSeattle_019edbbc-1fab-7250-9a80-f2e09d8b9dd5" xlink:href="bxp-20260630.xsd#bxp_PerOccurrenceLimitOfEarthquakeInsuranceSeattle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_PerOccurrenceLimitOfEarthquakeInsuranceSeattle_019edbbc-1fab-7250-9a80-f2e09d8b9dd5" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AnnualAggregateLimitOfEarthquakeInsuranceSeattle_019edbbc-1fab-70ee-af2f-ea53723bdc35" xlink:href="bxp-20260630.xsd#bxp_AnnualAggregateLimitOfEarthquakeInsuranceSeattle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_AnnualAggregateLimitOfEarthquakeInsuranceSeattle_019edbbc-1fab-70ee-af2f-ea53723bdc35" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySeattle_019edbbc-1fab-72c4-a80c-661ce670269a" xlink:href="bxp-20260630.xsd#bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySeattle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_EarthquakeDeductibleInsurancePercentageOfValueOfTheAffectedPropertySeattle_019edbbc-1fab-72c4-a80c-661ce670269a" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary_019edbbc-1fab-7c80-9d58-df76738a6568" xlink:href="bxp-20260630.xsd#bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_OperatingPartnershipGuaranteeToCoverLiabilitiesOfSubsidiary_019edbbc-1fab-7c80-9d58-df76738a6568" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NumberOfMezzanineLoanReceivablesHeld_019edbbc-1fab-7a6f-a9f3-6c6e8e9a878b" xlink:href="bxp-20260630.xsd#bxp_NumberOfMezzanineLoanReceivablesHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_CommitmentsAndContingenciesLineItems_019edbbc-1eca-79c0-9eaf-b7c375bccb60" xlink:to="loc_bxp_NumberOfMezzanineLoanReceivablesHeld_019edbbc-1fab-7a6f-a9f3-6c6e8e9a878b" xlink:type="arc" order="33"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/ScheduleofNoncontrollingInterestsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#ScheduleofNoncontrollingInterestsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/ScheduleofNoncontrollingInterestsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7ddc-b458-5e3d562aa8e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7e9a-99da-4a05ea49f683" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7ddc-b458-5e3d562aa8e4" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7e9a-99da-4a05ea49f683" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7cba-afe1-8ac566465064" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7e9a-99da-4a05ea49f683" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7cba-afe1-8ac566465064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7cba-afe1-8ac566465064_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7cba-afe1-8ac566465064" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7cba-afe1-8ac566465064_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-72d2-9970-1b671547e31d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7cba-afe1-8ac566465064" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-72d2-9970-1b671547e31d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7b48-813b-f68ddf796aab" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-72d2-9970-1b671547e31d" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7b48-813b-f68ddf796aab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7866-abe0-32c6ec5f5db8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7e9a-99da-4a05ea49f683" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7866-abe0-32c6ec5f5db8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7866-abe0-32c6ec5f5db8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7866-abe0-32c6ec5f5db8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7866-abe0-32c6ec5f5db8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7866-abe0-32c6ec5f5db8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitsMember_019edbbc-1fab-740a-9cfc-725ec96a2414" xlink:href="bxp-20260630.xsd#bxp_OpUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_OpUnitsMember_019edbbc-1fab-740a-9cfc-725ec96a2414" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPUnitsMember_019edbbc-1fab-79a5-9d21-276f63755fb6" xlink:href="bxp-20260630.xsd#bxp_LTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_LTIPUnitsMember_019edbbc-1fab-79a5-9d21-276f63755fb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyFourMember_019edbbc-1fab-71f7-a32d-8596a9bd9f4a" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyFourMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyFourMember_019edbbc-1fab-71f7-a32d-8596a9bd9f4a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyFiveMember_019edbbc-1fab-79e9-bade-62a55d790906" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyFiveMember_019edbbc-1fab-79e9-bade-62a55d790906" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7921-9abe-22ab58b90fb5" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7921-9abe-22ab58b90fb5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_A2025OPPMember_019edbbc-1fab-7859-afbc-08271820d1ae" xlink:href="bxp-20260630.xsd#bxp_A2025OPPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_A2025OPPMember_019edbbc-1fab-7859-afbc-08271820d1ae" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_A2012OPPAnd20132023MYLTIPMember_019edbbc-1fab-7ea0-ad37-a3dc1d52f16d" xlink:href="bxp-20260630.xsd#bxp_A2012OPPAnd20132023MYLTIPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_A2012OPPAnd20132023MYLTIPMember_019edbbc-1fab-7ea0-ad37-a3dc1d52f16d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-70db-b9e7-5213bad26009" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-730e-8578-b9009c639ff5" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-70db-b9e7-5213bad26009" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019edbbc-1fab-77cc-9c23-d39e99b96593" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7ddc-b458-5e3d562aa8e4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019edbbc-1fab-77cc-9c23-d39e99b96593" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/MYLTIPSperformanceDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#MYLTIPSperformanceDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/MYLTIPSperformanceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-703f-9bab-6992507389ab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-703f-9bab-6992507389ab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7862-a9bd-391d04fa3dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-703f-9bab-6992507389ab" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7862-a9bd-391d04fa3dc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7862-a9bd-391d04fa3dc0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7862-a9bd-391d04fa3dc0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7862-a9bd-391d04fa3dc0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7ed4-8a69-0a82526dccd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7862-a9bd-391d04fa3dc0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7ed4-8a69-0a82526dccd8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-7124-a862-a6819b868621" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7ed4-8a69-0a82526dccd8" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-7124-a862-a6819b868621" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7f9e-a098-7eea0dccc22e" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-703f-9bab-6992507389ab" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7f9e-a098-7eea0dccc22e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7f9e-a098-7eea0dccc22e_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7f9e-a098-7eea0dccc22e" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7f9e-a098-7eea0dccc22e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7184-a228-e3d11fbce488" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7f9e-a098-7eea0dccc22e" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7184-a228-e3d11fbce488" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-739e-866a-a63f5d2763be" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7184-a228-e3d11fbce488" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-739e-866a-a63f5d2763be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Finalawardspercentageoftarget_019edbbc-1fab-7cf1-a07b-0340dd7c6483" xlink:href="bxp-20260630.xsd#bxp_Finalawardspercentageoftarget"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:to="loc_bxp_Finalawardspercentageoftarget_019edbbc-1fab-7cf1-a07b-0340dd7c6483" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-7553-9da1-73f40dc91916" xlink:href="bxp-20260630.xsd#bxp_ValueOfMyltipAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:to="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-7553-9da1-73f40dc91916" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019edbbc-1fab-795b-b015-0b078ebb7e31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019edbbc-1fab-795b-b015-0b078ebb7e31" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7a3f-994d-b9520b8be010" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c5f-93cf-802f01c6099b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7a3f-994d-b9520b8be010" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/NoncontrollingInterestsCommonUnitsDistributionsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#NoncontrollingInterestsCommonUnitsDistributionsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/NoncontrollingInterestsCommonUnitsDistributionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7a46-b323-ba9a9f8de42d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableTable_019edbbc-1fab-7875-b618-41f1336dabda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7a46-b323-ba9a9f8de42d" xlink:to="loc_us-gaap_DividendsPayableTable_019edbbc-1fab-7875-b618-41f1336dabda" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-774d-8a1e-82680ae199f7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DividendsPayableTable_019edbbc-1fab-7875-b618-41f1336dabda" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-774d-8a1e-82680ae199f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-774d-8a1e-82680ae199f7_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-774d-8a1e-82680ae199f7" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-774d-8a1e-82680ae199f7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7f43-a9f4-dd73fc252ec3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-774d-8a1e-82680ae199f7" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7f43-a9f4-dd73fc252ec3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-76e4-ac3b-cdcc0728962d" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7f43-a9f4-dd73fc252ec3" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-76e4-ac3b-cdcc0728962d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-78d6-b6f9-e3bb9750c635" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DividendsPayableTable_019edbbc-1fab-7875-b618-41f1336dabda" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-78d6-b6f9-e3bb9750c635" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-78d6-b6f9-e3bb9750c635_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-78d6-b6f9-e3bb9750c635" xlink:to="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-78d6-b6f9-e3bb9750c635_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7a45-8a41-9cc8b1eec838" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-78d6-b6f9-e3bb9750c635" xlink:to="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7a45-8a41-9cc8b1eec838" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitsAndLTIPUnitsMember_019edbbc-1fab-7fc8-98d9-862737043434" xlink:href="bxp-20260630.xsd#bxp_OpUnitsAndLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7a45-8a41-9cc8b1eec838" xlink:to="loc_bxp_OpUnitsAndLTIPUnitsMember_019edbbc-1fab-7fc8-98d9-862737043434" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-7bc1-8718-5ca94111b57c" xlink:href="bxp-20260630.xsd#bxp_UnvestedMYLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7a45-8a41-9cc8b1eec838" xlink:to="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-7bc1-8718-5ca94111b57c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableAmountPerShare_019edbbc-1fab-7c3e-bf3b-4c4bfc56fa97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableAmountPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7a46-b323-ba9a9f8de42d" xlink:to="loc_us-gaap_DividendsPayableAmountPerShare_019edbbc-1fab-7c3e-bf3b-4c4bfc56fa97" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019edbbc-1fab-7d29-b94e-d980df6397cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7a46-b323-ba9a9f8de42d" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019edbbc-1fab-7d29-b94e-d980df6397cb" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/CommonUnitsNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#CommonUnitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/CommonUnitsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7358-9bb0-7cf076afab72" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7358-9bb0-7cf076afab72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-7123-8045-f21504012973" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7358-9bb0-7cf076afab72" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-7123-8045-f21504012973" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7123-8045-f21504012973_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-7123-8045-f21504012973" xlink:to="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7123-8045-f21504012973_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7758-9015-e8e80ee00a5d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019edbbc-1fab-7123-8045-f21504012973" xlink:to="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7758-9015-e8e80ee00a5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitsMember_019edbbc-1fab-7f95-b58b-71f780a31e31" xlink:href="bxp-20260630.xsd#bxp_OpUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019edbbc-1fab-7758-9015-e8e80ee00a5d" xlink:to="loc_bxp_OpUnitsMember_019edbbc-1fab-7f95-b58b-71f780a31e31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7358-9bb0-7cf076afab72" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-77a0-92a8-e995cc57fbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7e4a-a965-cc8b5bdb5cf5" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-77a0-92a8-e995cc57fbe5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitsMember_019edbbc-1fab-7198-9391-7ea2ebb63eaf" xlink:href="bxp-20260630.xsd#bxp_OpUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-77a0-92a8-e995cc57fbe5" xlink:to="loc_bxp_OpUnitsMember_019edbbc-1fab-7198-9391-7ea2ebb63eaf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ConversionOf2012OPPUnitsAndMYLTIPSMember_019edbbc-1fab-74fb-ac9e-2d5dc718510b" xlink:href="bxp-20260630.xsd#bxp_ConversionOf2012OPPUnitsAndMYLTIPSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-77a0-92a8-e995cc57fbe5" xlink:to="loc_bxp_ConversionOf2012OPPUnitsAndMYLTIPSMember_019edbbc-1fab-74fb-ac9e-2d5dc718510b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75cb-97ff-84bc10790bea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7358-9bb0-7cf076afab72" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75cb-97ff-84bc10790bea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-75cb-97ff-84bc10790bea_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75cb-97ff-84bc10790bea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-75cb-97ff-84bc10790bea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-73c0-b1d9-efb60eb9e1af" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75cb-97ff-84bc10790bea" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-73c0-b1d9-efb60eb9e1af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-76ea-9daa-9692a5f5451c" xlink:href="bxp-20260630.xsd#bxp_UnvestedMYLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-73c0-b1d9-efb60eb9e1af" xlink:to="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-76ea-9daa-9692a5f5451c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019edbbc-1fab-7d14-b823-da2c8fbeebf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019edbbc-1fab-7d14-b823-da2c8fbeebf9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnvestedMYLTIPAnd2025OPPDistributionsAsComparedToTotalDistributionsPercentage_019edbbc-1fab-7900-b504-0c8816c84e92" xlink:href="bxp-20260630.xsd#bxp_UnvestedMYLTIPAnd2025OPPDistributionsAsComparedToTotalDistributionsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_bxp_UnvestedMYLTIPAnd2025OPPDistributionsAsComparedToTotalDistributionsPercentage_019edbbc-1fab-7900-b504-0c8816c84e92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RestrictionOnRedemption_019edbbc-1fab-79c8-81ed-23003c0445f1" xlink:href="bxp-20260630.xsd#bxp_RestrictionOnRedemption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_bxp_RestrictionOnRedemption_019edbbc-1fab-79c8-81ed-23003c0445f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_OpUnitEquivalenceToCommonStock_019edbbc-1fab-7968-b942-92581e884f01" xlink:href="bxp-20260630.xsd#bxp_OpUnitEquivalenceToCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_bxp_OpUnitEquivalenceToCommonStock_019edbbc-1fab-7968-b942-92581e884f01" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019edbbc-1fab-7be5-8aa4-9d5d41b66715" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_us-gaap_SharePrice_019edbbc-1fab-7be5-8aa4-9d5d41b66715" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount_019edbbc-1fab-7ba7-9c2f-53a458fc3af7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetLineItems_019edbbc-1fab-7cbf-98da-f159ef5a69b7" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityPreferredCarryingAmount_019edbbc-1fab-7ba7-9c2f-53a458fc3af7" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/NoncontrollingInterestsPropertyPartnershipsNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#NoncontrollingInterestsPropertyPartnershipsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/NoncontrollingInterestsPropertyPartnershipsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7ea3-ac50-b6e8c2edcdf4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7b80-b836-da5087de9a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7ea3-ac50-b6e8c2edcdf4" xlink:to="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7b80-b836-da5087de9a1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-768d-92d3-62959d1c4d55" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7b80-b836-da5087de9a1e" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-768d-92d3-62959d1c4d55" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-768d-92d3-62959d1c4d55_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-768d-92d3-62959d1c4d55" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-768d-92d3-62959d1c4d55_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7347-805d-82f3fdc87d28" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-768d-92d3-62959d1c4d55" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7347-805d-82f3fdc87d28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeFourThreeMadisonAvenueMember_019edbbc-1fab-7b0f-ab56-bb519321dd78" xlink:href="bxp-20260630.xsd#bxp_ThreeFourThreeMadisonAvenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7347-805d-82f3fdc87d28" xlink:to="loc_bxp_ThreeFourThreeMadisonAvenueMember_019edbbc-1fab-7b0f-ab56-bb519321dd78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConsolidationLessThanWhollyOwnedSubsidiaryParentOwnershipInterestEffectsOfChangesNetTable_019edbbc-1fab-7b80-b836-da5087de9a1e" xlink:to="loc_srt_OwnershipAxis_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68" xlink:to="loc_srt_OwnershipDomain_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1fab-75bc-b83b-d920853d0c26" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1fab-7f1a-8129-ddf4d5eb0f68" xlink:to="loc_srt_OwnershipDomain_019edbbc-1fab-75bc-b83b-d920853d0c26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MinorityInterestMember_019edbbc-1fab-7a3b-ab38-212d71fead9a" xlink:href="bxp-20260630.xsd#bxp_MinorityInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1fab-75bc-b83b-d920853d0c26" xlink:to="loc_bxp_MinorityInterestMember_019edbbc-1fab-7a3b-ab38-212d71fead9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestInLimitedPartnerships_019edbbc-1fab-7858-8958-b9bbb2f6b334" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterestInLimitedPartnerships"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019edbbc-1fab-7ea3-ac50-b6e8c2edcdf4" xlink:to="loc_us-gaap_MinorityInterestInLimitedPartnerships_019edbbc-1fab-7858-8958-b9bbb2f6b334" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockholdersEquityPartnersCapitalNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockholdersEquityPartnersCapitalNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockholdersEquityPartnersCapitalNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019edbbc-1fab-7c64-9d25-38afc1561275" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019edbbc-1fab-7c64-9d25-38afc1561275" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019edbbc-1fab-7c64-9d25-38afc1561275" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7c98-964b-a475ad8805db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78b9-b9a6-f1f4a42ff4e8" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7c98-964b-a475ad8805db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AtmProgramMember_019edbbc-1fab-70a3-9dd6-f4cc92919007" xlink:href="bxp-20260630.xsd#bxp_AtmProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7c98-964b-a475ad8805db" xlink:to="loc_bxp_AtmProgramMember_019edbbc-1fab-70a3-9dd6-f4cc92919007" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1fab-7774-8cd5-3a5dec8a0a96" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019edbbc-1fab-7774-8cd5-3a5dec8a0a96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019edbbc-1fab-79de-92fc-3f327eed0127" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019edbbc-1fab-79de-92fc-3f327eed0127" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019edbbc-1fab-714f-b9ff-132439597026" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019edbbc-1fab-714f-b9ff-132439597026" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AtMarketStockOfferingProgramAggregateValueOfCommonStock_019edbbc-1fab-72da-a943-a5d990cf3046" xlink:href="bxp-20260630.xsd#bxp_AtMarketStockOfferingProgramAggregateValueOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_bxp_AtMarketStockOfferingProgramAggregateValueOfCommonStock_019edbbc-1fab-72da-a943-a5d990cf3046" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_AtMarketStockOfferingProgramMaximumLengthOfSaleinyears_019edbbc-1fab-7647-bba8-2367f4725e92" xlink:href="bxp-20260630.xsd#bxp_AtMarketStockOfferingProgramMaximumLengthOfSaleinyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_bxp_AtMarketStockOfferingProgramMaximumLengthOfSaleinyears_019edbbc-1fab-7647-bba8-2367f4725e92" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019edbbc-1fab-733e-8237-34af90dc6c14" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_CommonStockSharesIssued_019edbbc-1fab-733e-8237-34af90dc6c14" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesIssued1_019edbbc-1fab-7848-ae0f-0c27adcb5b37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConversionOfStockSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019edbbc-1fab-76ab-829f-49e03a2cdc4f" xlink:to="loc_us-gaap_ConversionOfStockSharesIssued1_019edbbc-1fab-7848-ae0f-0c27adcb5b37" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockholdersEquityPartnersCapitalDividendsDistributionsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockholdersEquityPartnersCapitalDividendsDistributionsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockholdersEquityPartnersCapitalDividendsDistributionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7393-a26c-b5cbc7492cf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1fab-7c72-86dd-496284a25646" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7393-a26c-b5cbc7492cf9" xlink:to="loc_dei_EntitiesTable_019edbbc-1fab-7c72-86dd-496284a25646" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7f5c-9352-66084d3c6332" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1fab-7c72-86dd-496284a25646" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7f5c-9352-66084d3c6332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7f5c-9352-66084d3c6332_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7f5c-9352-66084d3c6332" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7f5c-9352-66084d3c6332_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7392-9b6d-e6507387eca4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7f5c-9352-66084d3c6332" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7392-9b6d-e6507387eca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7963-aed8-41628c435f2d" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7392-9b6d-e6507387eca4" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7963-aed8-41628c435f2d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableAmountPerShare_019edbbc-1fab-7d21-9a21-46aa6e61fddf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsPayableAmountPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7393-a26c-b5cbc7492cf9" xlink:to="loc_us-gaap_DividendsPayableAmountPerShare_019edbbc-1fab-7d21-9a21-46aa6e61fddf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019edbbc-1fab-7bb4-9976-c9db4d401b5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DividendsPayableLineItems_019edbbc-1fab-7393-a26c-b5cbc7492cf9" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019edbbc-1fab-7bb4-9976-c9db4d401b5f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SegmentInformationNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SegmentInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7113-bd13-493c05eeff43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-78ec-8737-9ce7f2d9210e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7113-bd13-493c05eeff43" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-78ec-8737-9ce7f2d9210e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SegmentInformationScheduleOfReconciliationOfNetOperatingIncomeToNetIncomeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SegmentInformationScheduleOfReconciliationOfNetOperatingIncomeToNetIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SegmentInformationScheduleOfReconciliationOfNetOperatingIncomeToNetIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78dc-8d46-31555dc8f8a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78dc-8d46-31555dc8f8a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-78dc-8d46-31555dc8f8a8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78dc-8d46-31555dc8f8a8" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-78dc-8d46-31555dc8f8a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7740-b123-47ae128e31e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-78dc-8d46-31555dc8f8a8" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7740-b123-47ae128e31e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1fab-7165-8528-90d393be1f98" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestpropertypartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7740-b123-47ae128e31e6" xlink:to="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1fab-7165-8528-90d393be1f98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019edbbc-1fab-767c-a5dc-430ffec9d4aa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:to="loc_srt_ProductOrServiceAxis_019edbbc-1fab-767c-a5dc-430ffec9d4aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-767c-a5dc-430ffec9d4aa_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-767c-a5dc-430ffec9d4aa" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-767c-a5dc-430ffec9d4aa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-736b-b469-a5e0d885cf0e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-767c-a5dc-430ffec9d4aa" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-736b-b469-a5e0d885cf0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementServiceMember_019edbbc-1fab-7415-bc9d-1621083ef0e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ManagementServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-736b-b469-a5e0d885cf0e" xlink:to="loc_us-gaap_ManagementServiceMember_019edbbc-1fab-7415-bc9d-1621083ef0e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7778-bacd-e79923f98dbb" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7778-bacd-e79923f98dbb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7778-bacd-e79923f98dbb_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7778-bacd-e79923f98dbb" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7778-bacd-e79923f98dbb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7696-92a1-bb15a27ae639" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7778-bacd-e79923f98dbb" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7696-92a1-bb15a27ae639" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7a44-a848-58f4e7a84b48" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7696-92a1-bb15a27ae639" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7a44-a848-58f4e7a84b48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1fab-7424-8226-0e2ed5e352e3" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7696-92a1-bb15a27ae639" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1fab-7424-8226-0e2ed5e352e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_019edbbc-1fab-734e-832c-06b2a139c527" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7ad0-ae24-9741330980a2" xlink:to="loc_srt_ConsolidationItemsAxis_019edbbc-1fab-734e-832c-06b2a139c527" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019edbbc-1fab-734e-832c-06b2a139c527_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_019edbbc-1fab-734e-832c-06b2a139c527" xlink:to="loc_srt_ConsolidationItemsDomain_019edbbc-1fab-734e-832c-06b2a139c527_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_019edbbc-1fab-76e7-bfcf-80e229d3568d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_019edbbc-1fab-734e-832c-06b2a139c527" xlink:to="loc_srt_ConsolidationItemsDomain_019edbbc-1fab-76e7-bfcf-80e229d3568d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_019edbbc-1fab-7295-bd2a-efb8105ae6ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_019edbbc-1fab-76e7-bfcf-80e229d3568d" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_019edbbc-1fab-7295-bd2a-efb8105ae6ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NetOperatingIncome_019edbbc-1fab-77b2-b554-44855c4b6e91" xlink:href="bxp-20260630.xsd#bxp_NetOperatingIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_bxp_NetOperatingIncome_019edbbc-1fab-77b2-b554-44855c4b6e91" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-7ab9-8f11-2ddc97e17e95" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-7ab9-8f11-2ddc97e17e95" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1fab-7aef-a5e5-88d1ea6c2c38" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019edbbc-1fab-7aef-a5e5-88d1ea6c2c38" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1fab-73a3-9e9d-d182ad34594e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDispositionOfAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_019edbbc-1fab-73a3-9e9d-d182ad34594e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndOtherIncome_019edbbc-1fab-7e6f-afeb-c2e749bfddf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestAndOtherIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_InterestAndOtherIncome_019edbbc-1fab-7e6f-afeb-c2e749bfddf1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnrealizedGainLossOnInvestments_019edbbc-1fab-774a-b11c-b823930d0e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UnrealizedGainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_UnrealizedGainLossOnInvestments_019edbbc-1fab-774a-b11c-b823930d0e4d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019edbbc-1fab-7898-b6ba-6c0bce41e049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_GrossProfit_019edbbc-1fab-7898-b6ba-6c0bce41e049" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019edbbc-1fab-7993-ad23-76d89189a3fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019edbbc-1fab-7993-ad23-76d89189a3fc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1fab-7601-9f4f-97f01a478dd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1fab-7601-9f4f-97f01a478dd1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1fab-7f0c-ac00-d95b7f1bda6e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_019edbbc-1fab-7f0c-ac00-d95b7f1bda6e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019edbbc-1fab-786f-9ace-7a90862cb95a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_DepreciationAndAmortization_019edbbc-1fab-786f-9ace-7a90862cb95a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1fab-75a4-8bbf-9cb6003d3f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_019edbbc-1fab-75a4-8bbf-9cb6003d3f2a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnInvestments_019edbbc-1fab-744e-939b-62b91fbe40fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_GainLossOnInvestments_019edbbc-1fab-744e-939b-62b91fbe40fd" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_019edbbc-1fab-7320-9f81-83aa77cc8624" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_AssetImpairmentCharges_019edbbc-1fab-7320-9f81-83aa77cc8624" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1fab-7928-8f17-a48f75e5c8e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_GainsLossesOnExtinguishmentOfDebt_019edbbc-1fab-7928-8f17-a48f75e5c8e7" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019edbbc-1fab-778f-ae10-3204a48e0c46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_InterestExpense_019edbbc-1fab-778f-ae10-3204a48e0c46" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019edbbc-1fab-76aa-8808-fc210afee266" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_ProfitLoss_019edbbc-1fab-76aa-8808-fc210afee266" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable_019edbbc-1fab-7388-8081-5f76c532d001" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossLimitedPartnershipsNonredeemable_019edbbc-1fab-7388-8081-5f76c532d001" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_019edbbc-1fab-7f32-9e9e-9968d9882bd3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable_019edbbc-1fab-7f32-9e9e-9968d9882bd3" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019edbbc-1fab-771e-90db-7a1ebb5dd1e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7d7a-8f9c-000f02288a2b" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019edbbc-1fab-771e-90db-7a1ebb5dd1e9" xlink:type="arc" order="19"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SegmentInformationScheduleofReconciliationofRevenuetoRentalRevenueDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SegmentInformationScheduleofReconciliationofRevenuetoRentalRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SegmentInformationScheduleofReconciliationofRevenuetoRentalRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7a1d-ae00-eb042d7dc05d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-76fa-af33-ab22ee4e7e78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7a1d-ae00-eb042d7dc05d" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-76fa-af33-ab22ee4e7e78" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019edbbc-1fab-7464-a815-ef5fb65672f7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-76fa-af33-ab22ee4e7e78" xlink:to="loc_srt_ProductOrServiceAxis_019edbbc-1fab-7464-a815-ef5fb65672f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7464-a815-ef5fb65672f7_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-7464-a815-ef5fb65672f7" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7464-a815-ef5fb65672f7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7a51-99d5-cd525e8cf015" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-7464-a815-ef5fb65672f7" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7a51-99d5-cd525e8cf015" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManagementServiceMember_019edbbc-1fab-7e99-a33d-146002800987" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ManagementServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7a51-99d5-cd525e8cf015" xlink:to="loc_us-gaap_ManagementServiceMember_019edbbc-1fab-7e99-a33d-146002800987" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateOtherMember_019edbbc-1fab-73ce-8ffb-5ffe67e6ccf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RealEstateOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7a51-99d5-cd525e8cf015" xlink:to="loc_us-gaap_RealEstateOtherMember_019edbbc-1fab-73ce-8ffb-5ffe67e6ccf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019edbbc-1fab-7be1-8351-3d878ccad2bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7a1d-ae00-eb042d7dc05d" xlink:to="loc_us-gaap_Revenues_019edbbc-1fab-7be1-8351-3d878ccad2bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-75e6-8d0a-fb44164bb6b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7a1d-ae00-eb042d7dc05d" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-75e6-8d0a-fb44164bb6b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalRevenueTotal_019edbbc-1fab-7474-80b1-daecc5ee25a9" xlink:href="bxp-20260630.xsd#bxp_RentalRevenueTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7a1d-ae00-eb042d7dc05d" xlink:to="loc_bxp_RentalRevenueTotal_019edbbc-1fab-7474-80b1-daecc5ee25a9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SegmentInformationScheduleOfSegmentReportingByGeographicAreaAndPropertyTypeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SegmentInformationScheduleOfSegmentReportingByGeographicAreaAndPropertyTypeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SegmentInformationScheduleOfSegmentReportingByGeographicAreaAndPropertyTypeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_019edbbc-1fab-770a-ae97-9eeb3b72ad91" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:to="loc_srt_OwnershipAxis_019edbbc-1fab-770a-ae97-9eeb3b72ad91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1fab-770a-ae97-9eeb3b72ad91_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_019edbbc-1fab-770a-ae97-9eeb3b72ad91" xlink:to="loc_srt_OwnershipDomain_019edbbc-1fab-770a-ae97-9eeb3b72ad91_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_019edbbc-1fab-7818-a089-b9f80fd42866" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_019edbbc-1fab-770a-ae97-9eeb3b72ad91" xlink:to="loc_srt_OwnershipDomain_019edbbc-1fab-7818-a089-b9f80fd42866" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_CompanysShareMember_019edbbc-1fab-7d36-819d-fc6550ad5f4a" xlink:href="bxp-20260630.xsd#bxp_CompanysShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_019edbbc-1fab-7818-a089-b9f80fd42866" xlink:to="loc_bxp_CompanysShareMember_019edbbc-1fab-7d36-819d-fc6550ad5f4a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-756e-b7e1-ea39b86aeed4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-756e-b7e1-ea39b86aeed4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-756e-b7e1-ea39b86aeed4_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-756e-b7e1-ea39b86aeed4" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-756e-b7e1-ea39b86aeed4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7012-86ab-0ba08b06a2d5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-756e-b7e1-ea39b86aeed4" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7012-86ab-0ba08b06a2d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1fab-7159-8e24-8433e925c8e7" xlink:href="bxp-20260630.xsd#bxp_UnconsolidatedJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7012-86ab-0ba08b06a2d5" xlink:to="loc_bxp_UnconsolidatedJointVenturesMember_019edbbc-1fab-7159-8e24-8433e925c8e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7bca-bc68-cf94d28aed47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7bca-bc68-cf94d28aed47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7bca-bc68-cf94d28aed47_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7bca-bc68-cf94d28aed47" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7bca-bc68-cf94d28aed47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7bd1-b861-51a6bd38457c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019edbbc-1fab-7bca-bc68-cf94d28aed47" xlink:to="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7bd1-b861-51a6bd38457c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1fab-71f1-b11e-5cec68719567" xlink:href="bxp-20260630.xsd#bxp_NoncontrollinginterestpropertypartnershipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019edbbc-1fab-7bd1-b861-51a6bd38457c" xlink:to="loc_bxp_NoncontrollinginterestpropertypartnershipsMember_019edbbc-1fab-71f1-b11e-5cec68719567" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019edbbc-1fab-715d-83f2-e0fcdd6d640e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:to="loc_srt_ProductOrServiceAxis_019edbbc-1fab-715d-83f2-e0fcdd6d640e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-715d-83f2-e0fcdd6d640e_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-715d-83f2-e0fcdd6d640e" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-715d-83f2-e0fcdd6d640e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7b54-af07-13f1eacc2e96" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019edbbc-1fab-715d-83f2-e0fcdd6d640e" xlink:to="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7b54-af07-13f1eacc2e96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_HotelMember_019edbbc-1fab-7245-8f1a-dbe87d7dca82" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_HotelMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019edbbc-1fab-7b54-af07-13f1eacc2e96" xlink:to="loc_srt_HotelMember_019edbbc-1fab-7245-8f1a-dbe87d7dca82" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019edbbc-1fab-7dab-8223-1c26bab357c7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_019edbbc-1fab-7f3d-b3ba-b64e11d72a35" xlink:to="loc_srt_StatementGeographicalAxis_019edbbc-1fab-7dab-8223-1c26bab357c7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-7dab-8223-1c26bab357c7_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019edbbc-1fab-7dab-8223-1c26bab357c7" xlink:to="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-7dab-8223-1c26bab357c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019edbbc-1fab-7dab-8223-1c26bab357c7" xlink:to="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonMember_019edbbc-1fab-7bd8-9c47-de510197fef0" xlink:href="bxp-20260630.xsd#bxp_BostonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_bxp_BostonMember_019edbbc-1fab-7bd8-9c47-de510197fef0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LosAngelesMember_019edbbc-1fab-776e-b201-61f637f9e183" xlink:href="bxp-20260630.xsd#bxp_LosAngelesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_bxp_LosAngelesMember_019edbbc-1fab-776e-b201-61f637f9e183" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_NY_019edbbc-1fab-7022-b99f-12075ffb316c" xlink:href="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd#stpr_NY"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_stpr_NY_019edbbc-1fab-7022-b99f-12075ffb316c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SanFranciscoMember_019edbbc-1fab-7585-a576-e204bf9daa61" xlink:href="bxp-20260630.xsd#bxp_SanFranciscoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_bxp_SanFranciscoMember_019edbbc-1fab-7585-a576-e204bf9daa61" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SeattleMember_019edbbc-1fab-7c85-9478-d04c355959e3" xlink:href="bxp-20260630.xsd#bxp_SeattleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_bxp_SeattleMember_019edbbc-1fab-7c85-9478-d04c355959e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_DC_019edbbc-1fab-75b1-b479-047807f59ea3" xlink:href="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd#stpr_DC"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019edbbc-1fab-742e-bcf2-d797e697c0d5" xlink:to="loc_stpr_DC_019edbbc-1fab-75b1-b479-047807f59ea3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalRevenueOffice_019edbbc-1fab-75ea-8fd0-cf483e29c5dc" xlink:href="bxp-20260630.xsd#bxp_RentalRevenueOffice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalRevenueOffice_019edbbc-1fab-75ea-8fd0-cf483e29c5dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalRevenueResidential_019edbbc-1fab-770f-aebd-4a8bb1809027" xlink:href="bxp-20260630.xsd#bxp_RentalRevenueResidential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalRevenueResidential_019edbbc-1fab-770f-aebd-4a8bb1809027" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-750d-a68c-7ee3c992c3c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_019edbbc-1fab-750d-a68c-7ee3c992c3c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalRevenueTotal_019edbbc-1fab-7ad7-a4e1-8ec49915090c" xlink:href="bxp-20260630.xsd#bxp_RentalRevenueTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalRevenueTotal_019edbbc-1fab-7ad7-a4e1-8ec49915090c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PercentageOfTotalRevenue_019edbbc-1fab-732b-a12e-5e486079febd" xlink:href="bxp-20260630.xsd#bxp_PercentageOfTotalRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_PercentageOfTotalRevenue_019edbbc-1fab-732b-a12e-5e486079febd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalExpensesOffice_019edbbc-1fab-72b5-9e80-d2507b96541a" xlink:href="bxp-20260630.xsd#bxp_RentalExpensesOffice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalExpensesOffice_019edbbc-1fab-72b5-9e80-d2507b96541a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalExpensesResidential_019edbbc-1fab-705d-a916-c85a20985f6a" xlink:href="bxp-20260630.xsd#bxp_RentalExpensesResidential"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalExpensesResidential_019edbbc-1fab-705d-a916-c85a20985f6a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1fab-7610-bd6c-f5d38c05e7f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_019edbbc-1fab-7610-bd6c-f5d38c05e7f1" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RentalExpensesOperatingExpensesTotal_019edbbc-1fab-7e4c-ba12-c929370c93be" xlink:href="bxp-20260630.xsd#bxp_RentalExpensesOperatingExpensesTotal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_RentalExpensesOperatingExpensesTotal_019edbbc-1fab-7e4c-ba12-c929370c93be" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PercentageOfTotalRentalExpenses_019edbbc-1fab-7457-a984-752ac7a54d29" xlink:href="bxp-20260630.xsd#bxp_PercentageOfTotalRentalExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_PercentageOfTotalRentalExpenses_019edbbc-1fab-7457-a984-752ac7a54d29" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_019edbbc-1fab-77f1-9309-65409d985035" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_us-gaap_GrossProfit_019edbbc-1fab-77f1-9309-65409d985035" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PercentageOfTotalNetOperatingIncome_019edbbc-1fab-7f88-bafe-c958fe74cf19" xlink:href="bxp-20260630.xsd#bxp_PercentageOfTotalNetOperatingIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_PercentageOfTotalNetOperatingIncome_019edbbc-1fab-7f88-bafe-c958fe74cf19" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_PercentageofCompanysShareofNetOperatingIncome_019edbbc-1fab-7a56-bb5d-6f793de95dad" xlink:href="bxp-20260630.xsd#bxp_PercentageofCompanysShareofNetOperatingIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_019edbbc-1fab-7008-af3a-e98039fa4e91" xlink:to="loc_bxp_PercentageofCompanysShareofNetOperatingIncome_019edbbc-1fab-7a56-bb5d-6f793de95dad" xlink:type="arc" order="12"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/EarningsPerShareCommonUnitNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#EarningsPerShareCommonUnitNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/EarningsPerShareCommonUnitNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1fab-7cc7-9647-e3eabaafa693" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1fab-7ed5-9c50-8f9c2104c613" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1fab-7cc7-9647-e3eabaafa693" xlink:to="loc_dei_EntitiesTable_019edbbc-1fab-7ed5-9c50-8f9c2104c613" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-72be-a7d8-3a8a3b06a471" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1fab-7ed5-9c50-8f9c2104c613" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-72be-a7d8-3a8a3b06a471" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-72be-a7d8-3a8a3b06a471_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-72be-a7d8-3a8a3b06a471" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-72be-a7d8-3a8a3b06a471_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7b00-ba74-0b4e7a3666cd" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-72be-a7d8-3a8a3b06a471" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7b00-ba74-0b4e7a3666cd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7d1b-ace7-a8fe7b9bc6c4" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7b00-ba74-0b4e7a3666cd" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7d1b-ace7-a8fe7b9bc6c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareReconciliationDisclosure_019edbbc-1fab-73ea-9baa-a97f1701a608" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareReconciliationDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1fab-7cc7-9647-e3eabaafa693" xlink:to="loc_us-gaap_EarningsPerShareReconciliationDisclosure_019edbbc-1fab-73ea-9baa-a97f1701a608" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/EarningsPerShareCommonUnitDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#EarningsPerShareCommonUnitDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/EarningsPerShareCommonUnitDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019edbbc-1fab-7c1f-89ac-e762383c1f97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019edbbc-1fab-71e8-9fc6-5032b21686e3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1fab-7c1f-89ac-e762383c1f97" xlink:to="loc_dei_EntitiesTable_019edbbc-1fab-71e8-9fc6-5032b21686e3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7800-af45-6686d961ad93" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019edbbc-1fab-71e8-9fc6-5032b21686e3" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7800-af45-6686d961ad93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7800-af45-6686d961ad93_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7800-af45-6686d961ad93" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7800-af45-6686d961ad93_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7bf8-8a5a-9b76e180a30a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7800-af45-6686d961ad93" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7bf8-8a5a-9b76e180a30a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-775f-a5f5-ba9aa8093b35" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7bf8-8a5a-9b76e180a30a" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-775f-a5f5-ba9aa8093b35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019edbbc-1fab-7c1f-89ac-e762383c1f97" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019edbbc-1fab-7f84-b173-9712081561ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019edbbc-1fab-7f84-b173-9712081561ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_019edbbc-1fab-7f36-aa1c-4151908862ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_ParticipatingSecuritiesDistributedAndUndistributedEarningsLossBasic_019edbbc-1fab-7f36-aa1c-4151908862ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_NetIncomeLossAvailableToCommonStockholdersAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasic_019edbbc-1fab-7ba4-b62f-54b3ce29a289" xlink:href="bxp-20260630.xsd#bxp_NetIncomeLossAvailableToCommonStockholdersAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_bxp_NetIncomeLossAvailableToCommonStockholdersAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasic_019edbbc-1fab-7ba4-b62f-54b3ce29a289" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_019edbbc-1fab-7da4-b58b-2d96137b5b1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_019edbbc-1fab-7da4-b58b-2d96137b5b1f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DilutiveSecurities_019edbbc-1fab-7922-bf3f-907cd86e5ae8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DilutiveSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_019edbbc-1fab-7da4-b58b-2d96137b5b1f" xlink:to="loc_us-gaap_DilutiveSecurities_019edbbc-1fab-7922-bf3f-907cd86e5ae8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1fab-7f03-8d82-97f19b3ffa12" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1fab-7f03-8d82-97f19b3ffa12" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019edbbc-1fab-72e0-b117-9d3ffdae829c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019edbbc-1fab-7f03-8d82-97f19b3ffa12" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019edbbc-1fab-72e0-b117-9d3ffdae829c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019edbbc-1fab-785e-ae8b-03fc44d6f538" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019edbbc-1fab-785e-ae8b-03fc44d6f538" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Allocationofundistributedearningstoparticipatingsecuritiesinshares_019edbbc-1fab-702e-a548-33ac314b3a36" xlink:href="bxp-20260630.xsd#bxp_Allocationofundistributedearningstoparticipatingsecuritiesinshares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_bxp_Allocationofundistributedearningstoparticipatingsecuritiesinshares_019edbbc-1fab-702e-a548-33ac314b3a36" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_WeightedAverageNumberOfSharesOutstandingAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasicinshares_019edbbc-1fab-71ec-8f3b-5db7d8beddb9" xlink:href="bxp-20260630.xsd#bxp_WeightedAverageNumberOfSharesOutstandingAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasicinshares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_bxp_WeightedAverageNumberOfSharesOutstandingAfterAllocationofUndistributedEarningstoParticipatingSecuritiesBasicinshares_019edbbc-1fab-71ec-8f3b-5db7d8beddb9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019edbbc-1fab-7e9e-a99f-f3f5d29eabbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_019edbbc-1fab-7e9e-a99f-f3f5d29eabbc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019edbbc-1fab-725c-9a15-1275bc359f20" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019edbbc-1fab-725c-9a15-1275bc359f20" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019edbbc-1fab-7635-aed1-0fcc0b8a9f47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_EarningsPerShareBasic_019edbbc-1fab-7635-aed1-0fcc0b8a9f47" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019edbbc-1fab-77fb-a11c-38eac72cc2cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019edbbc-1fab-77fb-a11c-38eac72cc2cf" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_RedeemableCommonUnits_019edbbc-1fab-74f4-90a0-4cf30db51ded" xlink:href="bxp-20260630.xsd#bxp_RedeemableCommonUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_bxp_RedeemableCommonUnits_019edbbc-1fab-74f4-90a0-4cf30db51ded" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019edbbc-1fab-7cd4-9930-923ca2855e8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019edbbc-1fab-7017-941f-d4a5901c0f30" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019edbbc-1fab-7cd4-9930-923ca2855e8b" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsVestedMYLTIPsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockOptionandIncentivePlanStockandUnitsVestedMYLTIPsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsVestedMYLTIPsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-767f-87b8-05fcc06cc599" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-767f-87b8-05fcc06cc599" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75bf-a3c8-cfb3446e15b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-767f-87b8-05fcc06cc599" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75bf-a3c8-cfb3446e15b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-75bf-a3c8-cfb3446e15b4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75bf-a3c8-cfb3446e15b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-75bf-a3c8-cfb3446e15b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-70cf-8647-ea6afa90db04" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-75bf-a3c8-cfb3446e15b4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-70cf-8647-ea6afa90db04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-773f-b5ce-df68796b69d5" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentyThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-70cf-8647-ea6afa90db04" xlink:to="loc_bxp_MYLTIPTwoThousandTwentyThreeMember_019edbbc-1fab-773f-b5ce-df68796b69d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-77a1-9ba7-3c43aaca63a7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-767f-87b8-05fcc06cc599" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-77a1-9ba7-3c43aaca63a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-77a1-9ba7-3c43aaca63a7_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-77a1-9ba7-3c43aaca63a7" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-77a1-9ba7-3c43aaca63a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7fb5-8e4d-d055592dac4b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-77a1-9ba7-3c43aaca63a7" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7fb5-8e4d-d055592dac4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-746f-88b9-5cda89456028" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7fb5-8e4d-d055592dac4b" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-746f-88b9-5cda89456028" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Finalawardspercentageoftarget_019edbbc-1fab-7bde-ad8a-359981011a31" xlink:href="bxp-20260630.xsd#bxp_Finalawardspercentageoftarget"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:to="loc_bxp_Finalawardspercentageoftarget_019edbbc-1fab-7bde-ad8a-359981011a31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-740f-a11d-82e04edcedd3" xlink:href="bxp-20260630.xsd#bxp_ValueOfMyltipAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:to="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-740f-a11d-82e04edcedd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019edbbc-1fab-7838-bb5b-a93ae6ed2668" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019edbbc-1fab-7838-bb5b-a93ae6ed2668" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7445-b36c-cf1652d8aa40" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-74ec-8e0c-e061066b24eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7445-b36c-cf1652d8aa40" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockOptionandIncentivePlan2026MYLTIPNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockOptionandIncentivePlan2026MYLTIPNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockOptionandIncentivePlan2026MYLTIPNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-74ef-9ed0-fd741f56b8d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-74ef-9ed0-fd741f56b8d3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-7325-826e-1e1cc0a4fb7b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-74ef-9ed0-fd741f56b8d3" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-7325-826e-1e1cc0a4fb7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7325-826e-1e1cc0a4fb7b_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7325-826e-1e1cc0a4fb7b" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7325-826e-1e1cc0a4fb7b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-7258-b8d6-b66c142725b9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-7325-826e-1e1cc0a4fb7b" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-7258-b8d6-b66c142725b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7810-a03a-1d6048e98092" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-7258-b8d6-b66c142725b9" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7810-a03a-1d6048e98092" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7dee-b3c8-e32dcac901ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-74ef-9ed0-fd741f56b8d3" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7dee-b3c8-e32dcac901ef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7dee-b3c8-e32dcac901ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7dee-b3c8-e32dcac901ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7dee-b3c8-e32dcac901ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7378-9d3c-cc94f5a6a464" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7dee-b3c8-e32dcac901ef" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7378-9d3c-cc94f5a6a464" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7405-a6b7-05dc7c4dd89f" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7378-9d3c-cc94f5a6a464" xlink:to="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7405-a6b7-05dc7c4dd89f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019edbbc-1fab-788a-9804-b15a53e747b8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-74ef-9ed0-fd741f56b8d3" xlink:to="loc_srt_RangeAxis_019edbbc-1fab-788a-9804-b15a53e747b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1fab-788a-9804-b15a53e747b8_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019edbbc-1fab-788a-9804-b15a53e747b8" xlink:to="loc_srt_RangeMember_019edbbc-1fab-788a-9804-b15a53e747b8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1fab-75ae-9611-fd3dbe17ef2a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019edbbc-1fab-788a-9804-b15a53e747b8" xlink:to="loc_srt_RangeMember_019edbbc-1fab-75ae-9611-fd3dbe17ef2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019edbbc-1fab-7fc7-a63d-c7be394fefb9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1fab-75ae-9611-fd3dbe17ef2a" xlink:to="loc_srt_MinimumMember_019edbbc-1fab-7fc7-a63d-c7be394fefb9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019edbbc-1fab-7809-b30f-e74c4ef353e3" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1fab-75ae-9611-fd3dbe17ef2a" xlink:to="loc_srt_MaximumMember_019edbbc-1fab-7809-b30f-e74c4ef353e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward_019edbbc-1fab-7b8c-8d63-d70dc72a759a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward_019edbbc-1fab-7b8c-8d63-d70dc72a759a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7acd-bdab-9dabb9a6e7cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019edbbc-1fab-7acd-bdab-9dabb9a6e7cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019edbbc-1fab-7a3c-bd30-3132705666c2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019edbbc-1fab-7a3c-bd30-3132705666c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedTarget_019edbbc-1fab-77e1-9c8a-ce53aba60e71" xlink:href="bxp-20260630.xsd#bxp_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedTarget"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_bxp_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedTarget_019edbbc-1fab-77e1-9c8a-ce53aba60e71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-7090-bdbc-2cc45a91b9b0" xlink:href="bxp-20260630.xsd#bxp_ValueOfMyltipAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7cc4-8bbf-262c0833f04b" xlink:to="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-7090-bdbc-2cc45a91b9b0" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsIssuancesDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockOptionandIncentivePlanStockandUnitsIssuancesDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsIssuancesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7e95-b606-6b3f5aa08085" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7e95-b606-6b3f5aa08085" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7e95-b606-6b3f5aa08085_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7e95-b606-6b3f5aa08085" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7e95-b606-6b3f5aa08085_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-773f-9c73-e3e41d3003f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7e95-b606-6b3f5aa08085" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-773f-9c73-e3e41d3003f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-785d-ba33-e2571ff1680c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-773f-9c73-e3e41d3003f9" xlink:to="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-785d-ba33-e2571ff1680c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPUnitsMember_019edbbc-1fab-7a73-bf83-132417dd4a07" xlink:href="bxp-20260630.xsd#bxp_LTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-773f-9c73-e3e41d3003f9" xlink:to="loc_bxp_LTIPUnitsMember_019edbbc-1fab-7a73-bf83-132417dd4a07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7a24-b7ab-b68c4e45fa23" xlink:href="bxp-20260630.xsd#bxp_MYLTIPTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-773f-9c73-e3e41d3003f9" xlink:to="loc_bxp_MYLTIPTwoThousandTwentySixMember_019edbbc-1fab-7a24-b7ab-b68c4e45fa23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019edbbc-1fab-78cf-8ba8-1b01470df063" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:to="loc_dei_LegalEntityAxis_019edbbc-1fab-78cf-8ba8-1b01470df063" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-78cf-8ba8-1b01470df063_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-78cf-8ba8-1b01470df063" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-78cf-8ba8-1b01470df063_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019edbbc-1fab-75f5-95ee-dc8b939a0413" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019edbbc-1fab-78cf-8ba8-1b01470df063" xlink:to="loc_dei_EntityDomain_019edbbc-1fab-75f5-95ee-dc8b939a0413" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7658-9c3d-3563d0f37dda" xlink:href="bxp-20260630.xsd#bxp_BostonPropertiesLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019edbbc-1fab-75f5-95ee-dc8b939a0413" xlink:to="loc_bxp_BostonPropertiesLimitedPartnershipMember_019edbbc-1fab-7658-9c3d-3563d0f37dda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019edbbc-1fab-7e81-8ec6-932664277fcd" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:to="loc_srt_RangeAxis_019edbbc-1fab-7e81-8ec6-932664277fcd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1fab-7e81-8ec6-932664277fcd_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019edbbc-1fab-7e81-8ec6-932664277fcd" xlink:to="loc_srt_RangeMember_019edbbc-1fab-7e81-8ec6-932664277fcd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019edbbc-1fab-7c9b-961d-3a937da983bc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019edbbc-1fab-7e81-8ec6-932664277fcd" xlink:to="loc_srt_RangeMember_019edbbc-1fab-7c9b-961d-3a937da983bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019edbbc-1fab-7fad-a0b3-60c9e1b9652d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019edbbc-1fab-7c9b-961d-3a937da983bc" xlink:to="loc_srt_MaximumMember_019edbbc-1fab-7fad-a0b3-60c9e1b9652d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7508-9182-b6ff3ab7a096" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-727d-aa3e-7adc95e69d26" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7508-9182-b6ff3ab7a096" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7508-9182-b6ff3ab7a096_default" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7508-9182-b6ff3ab7a096" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7508-9182-b6ff3ab7a096_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7cf9-82fd-a1aaaf7755b7" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7508-9182-b6ff3ab7a096" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7cf9-82fd-a1aaaf7755b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPAnd2026MYLTIPUnitsMember_019edbbc-1fab-772d-84f4-610f72038a42" xlink:href="bxp-20260630.xsd#bxp_LTIPAnd2026MYLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7cf9-82fd-a1aaaf7755b7" xlink:to="loc_bxp_LTIPAnd2026MYLTIPUnitsMember_019edbbc-1fab-772d-84f4-610f72038a42" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019edbbc-1fab-7537-8898-8cc44fe8f054" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019edbbc-1fab-7537-8898-8cc44fe8f054" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_019edbbc-1fab-7b61-9eb1-11fbf6b8c04f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_019edbbc-1fab-7b61-9eb1-11fbf6b8c04f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_019edbbc-1fab-7129-84d0-bee2b7af2f91" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross_019edbbc-1fab-7129-84d0-bee2b7af2f91" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019edbbc-1fab-7684-8ea5-497be0e88d44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019edbbc-1fab-7684-8ea5-497be0e88d44" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-79c6-bae7-9844fc1ceb9c" xlink:href="bxp-20260630.xsd#bxp_ValueOfMyltipAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_bxp_ValueOfMyltipAwards_019edbbc-1fab-79c6-bae7-9844fc1ceb9c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_EmployeeAndDirectorPaymentPerShare_019edbbc-1fab-72e5-89c4-e0c5c7549692" xlink:href="bxp-20260630.xsd#bxp_EmployeeAndDirectorPaymentPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7ff4-b6be-db714d97fb4a" xlink:to="loc_bxp_EmployeeAndDirectorPaymentPerShare_019edbbc-1fab-72e5-89c4-e0c5c7549692" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsNarrativeDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#StockOptionandIncentivePlanStockandUnitsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/StockOptionandIncentivePlanStockandUnitsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c4e-a2b0-81fd3a0468c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-79a4-b10d-fd5049dea1f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c4e-a2b0-81fd3a0468c9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-79a4-b10d-fd5049dea1f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-79a4-b10d-fd5049dea1f2" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08_default" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:href="bxp-20260630.xsd#bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanAxis_019edbbc-1fab-7eb6-b8e5-9e4f2b01dd08" xlink:to="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-76d4-9cf5-c8af86cfc50d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:to="loc_us-gaap_RestrictedStockMember_019edbbc-1fab-76d4-9cf5-c8af86cfc50d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LTIPAnd2026MYLTIPUnitsMember_019edbbc-1fab-795b-93b9-069ed5572cc3" xlink:href="bxp-20260630.xsd#bxp_LTIPAnd2026MYLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:to="loc_bxp_LTIPAnd2026MYLTIPUnitsMember_019edbbc-1fab-795b-93b9-069ed5572cc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_LtipsincludingvestedMYLTIPSAndRestrictedStockMember_019edbbc-1fab-7aa3-ac4e-a7f9fccb441a" xlink:href="bxp-20260630.xsd#bxp_LtipsincludingvestedMYLTIPSAndRestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:to="loc_bxp_LtipsincludingvestedMYLTIPSAndRestrictedStockMember_019edbbc-1fab-7aa3-ac4e-a7f9fccb441a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-7c37-9034-a149ed5af9a7" xlink:href="bxp-20260630.xsd#bxp_UnvestedMYLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_bxp_StockOptionAndIncentivePlanAndStockRepurchasePlanDomain_019edbbc-1fab-71f7-88b6-6faeecef4eec" xlink:to="loc_bxp_UnvestedMYLTIPUnitsMember_019edbbc-1fab-7c37-9034-a149ed5af9a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7721-8d0a-78c23713c28b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019edbbc-1fab-79a4-b10d-fd5049dea1f2" xlink:to="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7721-8d0a-78c23713c28b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7721-8d0a-78c23713c28b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7721-8d0a-78c23713c28b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7721-8d0a-78c23713c28b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7fa5-98ac-12750abaec05" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019edbbc-1fab-7721-8d0a-78c23713c28b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7fa5-98ac-12750abaec05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_UnvestedRestrictedstockandLTIPUnitsMember_019edbbc-1fab-7160-bff1-7667619673c0" xlink:href="bxp-20260630.xsd#bxp_UnvestedRestrictedstockandLTIPUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019edbbc-1fab-7fa5-98ac-12750abaec05" xlink:to="loc_bxp_UnvestedRestrictedstockandLTIPUnitsMember_019edbbc-1fab-7160-bff1-7667619673c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019edbbc-1fab-7c13-a753-f4d0f8cf57fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c4e-a2b0-81fd3a0468c9" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019edbbc-1fab-7c13-a753-f4d0f8cf57fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019edbbc-1fab-72cd-966e-d2ba6ece0a73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c4e-a2b0-81fd3a0468c9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_019edbbc-1fab-72cd-966e-d2ba6ece0a73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019edbbc-1fab-7b28-84d9-dde191925ffb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019edbbc-1fab-7c4e-a2b0-81fd3a0468c9" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019edbbc-1fab-7b28-84d9-dde191925ffb" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.bxp.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="bxp-20260630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.bxp.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019edbbc-1fab-7c97-b866-fb46543f20be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019edbbc-1fab-7c97-b866-fb46543f20be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019edbbc-1fab-7c97-b866-fb46543f20be_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019edbbc-1fab-7c97-b866-fb46543f20be" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019edbbc-1fab-7c97-b866-fb46543f20be_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019edbbc-1fab-7f4f-8f10-3b0ece3c73c1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019edbbc-1fab-7c97-b866-fb46543f20be" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019edbbc-1fab-7f4f-8f10-3b0ece3c73c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019edbbc-1fab-7700-b149-5525088a4fd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019edbbc-1fab-7f4f-8f10-3b0ece3c73c1" xlink:to="loc_us-gaap_SubsequentEventMember_019edbbc-1fab-7700-b149-5525088a4fd8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-7257-9d75-b55162596984" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-7257-9d75-b55162596984" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7257-9d75-b55162596984_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-7257-9d75-b55162596984" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7257-9d75-b55162596984_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7df4-9358-6fbe5db6597d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis_019edbbc-1fab-7257-9d75-b55162596984" xlink:to="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7df4-9358-6fbe5db6597d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ThreeFourThreeMadisonAvenueMember_019fb99d-6c57-7e0b-8ebf-3698f3e5928a" xlink:href="bxp-20260630.xsd#bxp_ThreeFourThreeMadisonAvenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7df4-9358-6fbe5db6597d" xlink:to="loc_bxp_ThreeFourThreeMadisonAvenueMember_019fb99d-6c57-7e0b-8ebf-3698f3e5928a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_SumnerSquareMember_019fd217-86fd-7297-a63d-8b3c351d0c82" xlink:href="bxp-20260630.xsd#bxp_SumnerSquareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RealEstateAndAccumulatedDepreciationNameOfPropertyDomain_019edbbc-1fab-7df4-9358-6fbe5db6597d" xlink:to="loc_bxp_SumnerSquareMember_019fd217-86fd-7297-a63d-8b3c351d0c82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_019fb9a2-3868-7e82-b583-b07a797259d0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:to="loc_srt_StatementScenarioAxis_019fb9a2-3868-7e82-b583-b07a797259d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019fb9a2-3868-7e82-b583-b07a797259d0_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_019fb9a2-3868-7e82-b583-b07a797259d0" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019fb9a2-3868-7e82-b583-b07a797259d0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_019fb9a2-3868-73a2-9916-bc01891d9872" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_019fb9a2-3868-7e82-b583-b07a797259d0" xlink:to="loc_srt_ScenarioUnspecifiedDomain_019fb9a2-3868-73a2-9916-bc01891d9872" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScenarioPlanMember_019fb9a2-9a0b-73ff-bcdd-4c65ac883632" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScenarioPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_019fb9a2-3868-73a2-9916-bc01891d9872" xlink:to="loc_us-gaap_ScenarioPlanMember_019fb9a2-9a0b-73ff-bcdd-4c65ac883632" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019fb9f3-e8b6-7449-bb0f-946d4ef3536d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019edbbc-1fab-77ed-9f35-a3d88430d442" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019fb9f3-e8b6-7449-bb0f-946d4ef3536d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb9f3-e8b6-7449-bb0f-946d4ef3536d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb9f3-e8b6-7449-bb0f-946d4ef3536d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb9f3-e8b6-7449-bb0f-946d4ef3536d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019fb9f3-e8b6-7578-9232-b527e93ffded" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019fb9f3-e8b6-7449-bb0f-946d4ef3536d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019fb9f3-e8b6-7578-9232-b527e93ffded" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_019fb9f4-0dd2-70bf-9035-f435436c8097" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019fb9f3-e8b6-7578-9232-b527e93ffded" xlink:to="loc_us-gaap_ConstructionLoansMember_019fb9f4-0dd2-70bf-9035-f435436c8097" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019edbbc-1fab-70a0-b7f1-55fa781f24fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_NetRentableArea_019edbbc-1fab-70a0-b7f1-55fa781f24fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019fb99b-e004-77bf-964b-d616676c519f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019fb99b-e004-77bf-964b-d616676c519f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb99c-b48c-7440-a8c5-6fe2f0b9fdc3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019fb99c-b48c-7440-a8c5-6fe2f0b9fdc3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019fb9f3-0df3-7999-9ddb-0f389f9342c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount_019fb9f3-0df3-7999-9ddb-0f389f9342c9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_Numberofextensions_019fb9f3-b013-7312-8b18-8e8c98b694b3" xlink:href="bxp-20260630.xsd#bxp_Numberofextensions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_bxp_Numberofextensions_019fb9f3-b013-7312-8b18-8e8c98b694b3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ExtensionOptioninyears_019fbd41-f682-7984-b303-213a07cba605" xlink:href="bxp-20260630.xsd#bxp_ExtensionOptioninyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_bxp_ExtensionOptioninyears_019fbd41-f682-7984-b303-213a07cba605" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_019fc49f-f35c-782e-a713-3393dc0aec5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_019fc49f-f35c-782e-a713-3393dc0aec5a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_bxp_ContractualSalePrice_019fd217-86fd-7d9d-9884-5f3a7065a9ff" xlink:href="bxp-20260630.xsd#bxp_ContractualSalePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019edbbc-1fab-7fb1-9371-a114d3d7ee2c" xlink:to="loc_bxp_ContractualSalePrice_019fd217-86fd-7d9d-9884-5f3a7065a9ff" xlink:type="arc" order="7"/>
  </link:definitionLink>
</link:linkbase>
