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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019c9bd2-c475-7ca0-b2b4-514d6d671204,g:98c2e194-aec6-4d3a-96d3-6ff07f75d999-->
<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.nationalstorageaffiliates.com/role/COVERPAGE" xlink:type="simple" xlink:href="nsa-20260331.xsd#COVERPAGE"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/COVERPAGE" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_019c9bd2-c5c0-73b4-a5eb-6b6ec8cf9d3b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntitiesTable_019c9bd2-c5c0-73b4-a5eb-6b6ec8cf9d3b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c5c0-7993-ae86-ab0ef3611efa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_019c9bd2-c5c0-73b4-a5eb-6b6ec8cf9d3b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c5c0-7993-ae86-ab0ef3611efa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-7993-ae86-ab0ef3611efa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c5c0-7993-ae86-ab0ef3611efa" xlink:to="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-7993-ae86-ab0ef3611efa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-74e6-848f-aa49a8c0ca5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c5c0-7993-ae86-ab0ef3611efa" xlink:to="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-74e6-848f-aa49a8c0ca5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c9bd2-c5c0-74c0-942f-7b0eb538ca3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-74e6-848f-aa49a8c0ca5a" xlink:to="loc_us-gaap_CommonClassAMember_019c9bd2-c5c0-74c0-942f-7b0eb538ca3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemablePreferredStockMember_019c9bd2-c5c0-79e5-87b2-f65a73f268da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RedeemablePreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-74e6-848f-aa49a8c0ca5a" xlink:to="loc_us-gaap_RedeemablePreferredStockMember_019c9bd2-c5c0-79e5-87b2-f65a73f268da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_019c9bd2-c5c0-76d4-8e87-bda0d9c44d12" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesBPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c9bd2-c5c0-74e6-848f-aa49a8c0ca5a" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_019c9bd2-c5c0-76d4-8e87-bda0d9c44d12" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019c9bd2-c5c0-78f0-9952-50a35d96e5d3" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentType_019c9bd2-c5c0-78f0-9952-50a35d96e5d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019c9bd2-c5c0-788f-a4f8-d4a2d17b8f46" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentQuarterlyReport_019c9bd2-c5c0-788f-a4f8-d4a2d17b8f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019c9bd2-c5c0-7d40-a0e9-a3496e45a1bc" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentPeriodEndDate_019c9bd2-c5c0-7d40-a0e9-a3496e45a1bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019c9bd2-c5c0-7358-ba20-18b0a2afef9a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentTransitionReport_019c9bd2-c5c0-7358-ba20-18b0a2afef9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019c9bd2-c5c0-7720-b33c-f504dd716b00" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityFileNumber_019c9bd2-c5c0-7720-b33c-f504dd716b00" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019c9bd2-c5c0-7fa0-9205-f3afb8c8b38e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityRegistrantName_019c9bd2-c5c0-7fa0-9205-f3afb8c8b38e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019c9bd2-c5c0-7427-a9aa-2c05bbba1e19" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019c9bd2-c5c0-7427-a9aa-2c05bbba1e19" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019c9bd2-c5c0-7cef-b852-6e16fc0d8bc8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityTaxIdentificationNumber_019c9bd2-c5c0-7cef-b852-6e16fc0d8bc8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019c9bd2-c5c0-7b69-9157-f221dd3fb57a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityAddressAddressLine1_019c9bd2-c5c0-7b69-9157-f221dd3fb57a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019c9bd2-c5c0-764c-b533-5821a0c659dc" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityAddressCityOrTown_019c9bd2-c5c0-764c-b533-5821a0c659dc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019c9bd2-c5c0-71b4-a279-d0e46f79ce78" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityAddressStateOrProvince_019c9bd2-c5c0-71b4-a279-d0e46f79ce78" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019c9bd2-c5c0-73cc-b956-490e2320235d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityAddressPostalZipCode_019c9bd2-c5c0-73cc-b956-490e2320235d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019c9bd2-c5c0-78c9-a7ea-ea0d225e611d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_CityAreaCode_019c9bd2-c5c0-78c9-a7ea-ea0d225e611d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019c9bd2-c5c0-76d6-a944-92f8f3f05b88" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_LocalPhoneNumber_019c9bd2-c5c0-76d6-a944-92f8f3f05b88" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019c9bd2-c5c0-73e6-96a5-accd6b5492d1" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_Security12bTitle_019c9bd2-c5c0-73e6-96a5-accd6b5492d1" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019c9bd2-c5c0-769f-8df3-6e2f5281e362" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_TradingSymbol_019c9bd2-c5c0-769f-8df3-6e2f5281e362" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019c9bd2-c5c0-79c5-8d5f-ba4b25d67134" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_SecurityExchangeName_019c9bd2-c5c0-79c5-8d5f-ba4b25d67134" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019c9bd2-c5c0-7daa-b2ef-db59d6c60bfe" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityCurrentReportingStatus_019c9bd2-c5c0-7daa-b2ef-db59d6c60bfe" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019c9bd2-c5c0-7e13-9edb-8f1224f7c6af" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityInteractiveDataCurrent_019c9bd2-c5c0-7e13-9edb-8f1224f7c6af" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019c9bd2-c5c0-76dc-b3fa-1aed29be0edb" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityFilerCategory_019c9bd2-c5c0-76dc-b3fa-1aed29be0edb" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019c9bd2-c5c0-7dff-b0e1-aa3ff65a35e8" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntitySmallBusiness_019c9bd2-c5c0-7dff-b0e1-aa3ff65a35e8" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019c9bd2-c5c0-70fc-89b6-75c93c63cb60" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityEmergingGrowthCompany_019c9bd2-c5c0-70fc-89b6-75c93c63cb60" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019c9bd2-c5c0-7e22-a1ea-d7441f5e8475" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityShellCompany_019c9bd2-c5c0-7e22-a1ea-d7441f5e8475" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019c9bd2-c5c0-7763-bf49-67f52b46d021" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019c9bd2-c5c0-7763-bf49-67f52b46d021" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019c9bd2-c5c0-77a5-bce0-25a2755c0855" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_EntityCentralIndexKey_019c9bd2-c5c0-77a5-bce0-25a2755c0855" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019c9bd2-c5c0-7296-a39f-a1e27fe4a836" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_CurrentFiscalYearEndDate_019c9bd2-c5c0-7296-a39f-a1e27fe4a836" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019c9bd2-c5c0-7900-ae0b-2995974fed47" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentFiscalYearFocus_019c9bd2-c5c0-7900-ae0b-2995974fed47" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019c9bd2-c5c0-72f5-a839-de26f1997ffa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019c9bd2-c5c0-72f5-a839-de26f1997ffa" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019c9bd2-c5c0-7678-aed9-1c1c691a3033" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_019c9bd2-c5c0-7d58-9908-5ff55fcc69b5" xlink:to="loc_dei_AmendmentFlag_019c9bd2-c5c0-7678-aed9-1c1c691a3033" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="nsa-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c9bd2-c5c1-7aae-8aff-5805e2de1ad9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_StatementTable_019c9bd2-c5c1-7aae-8aff-5805e2de1ad9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-73d2-834c-d5bb1d848053" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c9bd2-c5c1-7aae-8aff-5805e2de1ad9" xlink:to="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-73d2-834c-d5bb1d848053" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-73d2-834c-d5bb1d848053_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-73d2-834c-d5bb1d848053" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-73d2-834c-d5bb1d848053_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7b07-b767-44700634f6ad" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-73d2-834c-d5bb1d848053" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7b07-b767-44700634f6ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c5c1-7898-8ddc-3aeb89b502e7" xlink:href="nsa-20260331.xsd#nsa_PropertyRelatedOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7b07-b767-44700634f6ad" xlink:to="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c5c1-7898-8ddc-3aeb89b502e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c5c1-7d40-ae45-1695f9a5a3af" xlink:href="nsa-20260331.xsd#nsa_ManagementFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7b07-b767-44700634f6ad" xlink:to="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c5c1-7d40-ae45-1695f9a5a3af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019c9bd2-c5c1-705d-8049-cb7b69b12fc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_RevenuesAbstract_019c9bd2-c5c1-705d-8049-cb7b69b12fc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c5c1-7822-9114-f70b9a8be24c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019c9bd2-c5c1-705d-8049-cb7b69b12fc1" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c5c1-7822-9114-f70b9a8be24c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c5c1-7da2-8a60-7f0d4eafcbcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019c9bd2-c5c1-705d-8049-cb7b69b12fc1" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c5c1-7da2-8a60-7f0d4eafcbcb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019c9bd2-c5c1-7ee5-b0cc-44a24073b083" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019c9bd2-c5c1-705d-8049-cb7b69b12fc1" xlink:to="loc_us-gaap_Revenues_019c9bd2-c5c1-7ee5-b0cc-44a24073b083" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_019c9bd2-c5c1-7d51-ae89-e5acaf18bff0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:to="loc_us-gaap_CostOfRevenue_019c9bd2-c5c1-7d51-ae89-e5acaf18bff0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019c9bd2-c5c1-7fe7-83e2-acb92fcf3fc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019c9bd2-c5c1-7fe7-83e2-acb92fcf3fc4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c5c1-7fe0-b2fe-0202be920841" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:to="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c5c1-7fe0-b2fe-0202be920841" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralExpense_019c9bd2-c5c1-72a2-af3b-665c680e617d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherGeneralExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:to="loc_us-gaap_OtherGeneralExpense_019c9bd2-c5c1-72a2-af3b-665c680e617d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019c9bd2-c5c1-739f-985f-640c520f18c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_019c9bd2-c5c1-7e0f-8cd6-c80e5c95dc03" xlink:to="loc_us-gaap_CostsAndExpenses_019c9bd2-c5c1-739f-985f-640c520f18c2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIncomeAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c5c1-7b6f-ac25-39793b9361ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c5c1-7b6f-ac25-39793b9361ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c9bd2-c5c1-70df-b571-83de4f21c21b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c9bd2-c5c1-70df-b571-83de4f21c21b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019c9bd2-c5c1-77f8-b362-634b74cdd925" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019c9bd2-c5c1-77f8-b362-634b74cdd925" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_019da029-5011-7963-89c3-60410ad3d6c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationIntegrationRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_019da029-5011-7963-89c3-60410ad3d6c8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c5c1-78ce-a4cb-9c99253c3d09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c5c1-78ce-a4cb-9c99253c3d09" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_019c9bd2-c5c1-7c26-8f34-b14d98f7ac32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_019c9bd2-c5c1-7c26-8f34-b14d98f7ac32" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_019c9bd2-c5c1-734b-9fa3-f0f072ca4c69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherIncomeAndExpensesAbstract_019c9bd2-c5c1-78a4-b25a-f772e1da1623" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_019c9bd2-c5c1-734b-9fa3-f0f072ca4c69" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9bd2-c5c1-723a-bad3-1664fb599410" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9bd2-c5c1-723a-bad3-1664fb599410" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019c9bd2-c5c1-7502-9052-18686996af21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019c9bd2-c5c1-7502-9052-18686996af21" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019c9bd2-c5c1-7d14-bb3c-400ea76e6bdd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_ProfitLoss_019c9bd2-c5c1-7d14-bb3c-400ea76e6bdd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019c9bd2-c5c1-70d6-a24c-030bed8b8481" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019c9bd2-c5c1-70d6-a24c-030bed8b8481" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c9bd2-c5c1-7e41-a305-0f850b1aaaf9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_NetIncomeLoss_019c9bd2-c5c1-7e41-a305-0f850b1aaaf9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_019c9bd2-c5c1-7fb7-95c3-df2081460bf6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendsIncomeStatementImpact"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_019c9bd2-c5c1-7fb7-95c3-df2081460bf6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019c9bd2-c5c1-798f-965b-fa094560dfe8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019c9bd2-c5c1-798f-965b-fa094560dfe8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019c9bd2-c5c1-7a8e-8dbe-fdf51e9a1ead" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:to="loc_us-gaap_EarningsPerShareBasic_019c9bd2-c5c1-7a8e-8dbe-fdf51e9a1ead" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019c9bd2-c5c1-72d5-b873-4c362710dacb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019c9bd2-c5c1-72d5-b873-4c362710dacb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019c9bd2-c5c1-7889-bd2e-2f5a1fc86bfd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019c9bd2-c5c1-7889-bd2e-2f5a1fc86bfd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019c9bd2-c5c1-7a53-a650-22129f2ba382" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019c9bd2-c5c1-7826-853e-c54d5f9ce343" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019c9bd2-c5c1-7a53-a650-22129f2ba382" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019c9bd2-c5c1-7aab-8c32-3316f37cc71b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-7d60-9be1-da3637658519" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019c9bd2-c5c1-7aab-8c32-3316f37cc71b" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="simple" xlink:href="nsa-20260331.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-75a9-a362-27ccae72f478" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019c9bd2-c5c1-709b-875d-266b195af4c0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-75a9-a362-27ccae72f478" xlink:to="loc_us-gaap_StatementTable_019c9bd2-c5c1-709b-875d-266b195af4c0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c5c1-736c-af2b-7b7110369e5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019c9bd2-c5c1-709b-875d-266b195af4c0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c5c1-736c-af2b-7b7110369e5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-736c-af2b-7b7110369e5f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c5c1-736c-af2b-7b7110369e5f" xlink:to="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-736c-af2b-7b7110369e5f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c5c1-736c-af2b-7b7110369e5f" xlink:to="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019c9bd2-c5c1-7cd5-b8d7-80196045cb6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_PreferredStockMember_019c9bd2-c5c1-7cd5-b8d7-80196045cb6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c9bd2-c5c1-7e26-9386-dc82f2182a30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_CommonStockMember_019c9bd2-c5c1-7e26-9386-dc82f2182a30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019c9bd2-c5c1-77a9-bb4f-5a1f22606a6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019c9bd2-c5c1-77a9-bb4f-5a1f22606a6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019c9bd2-c5c1-79bb-b247-7abaff900c2e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_RetainedEarningsMember_019c9bd2-c5c1-79bb-b247-7abaff900c2e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9bd2-c5c1-73c5-be50-b8b0714bcc21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_019c9bd2-c5c1-73c5-be50-b8b0714bcc21" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019c9bd2-c5c1-7d32-ac43-ad67a2fd76e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c5c1-7403-9900-b7fa259acaa9" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019c9bd2-c5c1-7d32-ac43-ad67a2fd76e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019c9bd2-c5c1-75a9-a362-27ccae72f478" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019c9bd2-c5c1-7b3a-868f-7142985f3fe6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019c9bd2-c5c1-7b3a-868f-7142985f3fe6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019c9bd2-c5c1-72d4-b5f4-b18f58b922bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019c9bd2-c5c1-72d4-b5f4-b18f58b922bc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019d68c0-d1e1-7e38-a300-962b8a4ce086" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019d68c0-d1e1-7e38-a300-962b8a4ce086" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019d68bb-51be-73e7-baf3-8a923685b9e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019d68bb-51be-73e7-baf3-8a923685b9e9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019d68bb-51be-7c59-a9dd-165cfc4802e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019d68bb-51be-7c59-a9dd-165cfc4802e0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019d68bb-51be-7ec7-90b1-4d3f67fe06db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019d68bb-51be-7ec7-90b1-4d3f67fe06db" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_019d68bb-51be-71ac-89ec-c24c130c57ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfUnits_019d68bb-51be-71ac-89ec-c24c130c57ae" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_EffectOfChangesInOwnershipForConsolidatedEntities_019d68bb-51be-7834-8cbb-8a03fc5993e6" xlink:href="nsa-20260331.xsd#nsa_EffectOfChangesInOwnershipForConsolidatedEntities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_nsa_EffectOfChangesInOwnershipForConsolidatedEntities_019d68bb-51be-7834-8cbb-8a03fc5993e6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition_019d68bb-51be-70aa-8f9b-c51b20fc5539" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationOtherLongtermIncentivePlansRequisiteServicePeriodRecognition_019d68bb-51be-70aa-8f9b-c51b20fc5539" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019d68bb-51be-7bbb-8a35-0e8ee2eb1540" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_019d68bb-51be-7bbb-8a35-0e8ee2eb1540" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_StockIssuedDuringPeriodSharesRestrictedStockAwardVestingAndForfeited_019d68bb-51be-7dd4-8ee9-951644a6bb9f" xlink:href="nsa-20260331.xsd#nsa_StockIssuedDuringPeriodSharesRestrictedStockAwardVestingAndForfeited"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_nsa_StockIssuedDuringPeriodSharesRestrictedStockAwardVestingAndForfeited_019d68bb-51be-7dd4-8ee9-951644a6bb9f" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_StockIssuedDuringPeriodValueRestrictedStockAwardVestingAndForfeited_019d68bb-51be-7a0a-b337-8229e109dde1" xlink:href="nsa-20260331.xsd#nsa_StockIssuedDuringPeriodValueRestrictedStockAwardVestingAndForfeited"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_nsa_StockIssuedDuringPeriodValueRestrictedStockAwardVestingAndForfeited_019d68bb-51be-7a0a-b337-8229e109dde1" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_019d68bb-51be-7185-a5a3-4e1cb8fd0c58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_019d68bb-51be-7185-a5a3-4e1cb8fd0c58" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPreferredStock_019d68bb-51be-70ad-851d-c5ec2e6934c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsPreferredStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_DividendsPreferredStock_019d68bb-51be-70ad-851d-c5ec2e6934c5" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_019d68bb-51be-73ca-892a-6f33a852e08f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_DividendsCommonStock_019d68bb-51be-73ca-892a-6f33a852e08f" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019d68bb-51be-7fbd-9b68-85c847486fed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_019d68bb-51be-7fbd-9b68-85c847486fed" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019d68bb-51be-7a90-8f23-7e608e0ad96f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_019d68bb-51be-7a90-8f23-7e608e0ad96f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019d68bb-51be-7692-89ac-cb191b1126c5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019c9bd2-c5c1-7883-a872-66ee6c8b6f37" xlink:to="loc_us-gaap_ProfitLoss_019d68bb-51be-7692-89ac-cb191b1126c5" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019d68c1-2126-7abc-9e63-a812cab359e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019c9bd2-c5c1-7e25-8028-7eb68c8d2ff4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019c9bd2-c5c1-740c-bd63-233ba5771098" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/ORGANIZATIONANDNATUREOFOPERATIONSDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#ORGANIZATIONANDNATUREOFOPERATIONSDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/ORGANIZATIONANDNATUREOFOPERATIONSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-74cd-a8bc-f20e221ec2ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019c9bd2-c5c1-7bce-ba60-48cb38d2a88c" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-74cd-a8bc-f20e221ec2ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConsolidatedPropertiesMember_019c9bd2-c5c1-7f1e-b20f-dd124ed8cda0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-74cd-a8bc-f20e221ec2ba" xlink:to="loc_us-gaap_ConsolidatedPropertiesMember_019c9bd2-c5c1-7f1e-b20f-dd124ed8cda0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019c9bd2-c5c1-7f9e-8401-479bb1825eab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019c9bd2-c5c1-74cd-a8bc-f20e221ec2ba" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019c9bd2-c5c1-7f9e-8401-479bb1825eab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c5c1-74a2-b8c9-39c536bef444" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c5c1-74a2-b8c9-39c536bef444" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c5c1-74a2-b8c9-39c536bef444_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c5c1-74a2-b8c9-39c536bef444" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c5c1-74a2-b8c9-39c536bef444_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c5c1-7169-887d-8506d87b862b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c5c1-74a2-b8c9-39c536bef444" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c5c1-7169-887d-8506d87b862b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c5c1-78eb-99ac-ac2efe6279f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c5c1-7169-887d-8506d87b862b" xlink:to="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c5c1-78eb-99ac-ac2efe6279f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c9bd2-c5c1-7d3a-a741-c376af9238fa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c9bd2-c5c1-7d3a-a741-c376af9238fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-7d3a-a741-c376af9238fa_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c9bd2-c5c1-7d3a-a741-c376af9238fa" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-7d3a-a741-c376af9238fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-70df-9c09-a4eba0944dab" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019c9bd2-c5c1-7d3a-a741-c376af9238fa" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-70df-9c09-a4eba0944dab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2018JointVentureMember_019c9bd2-c5c1-70d2-a04a-d39ec0831bac" xlink:href="nsa-20260331.xsd#nsa_A2018JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-70df-9c09-a4eba0944dab" xlink:to="loc_nsa_A2018JointVentureMember_019c9bd2-c5c1-70d2-a04a-d39ec0831bac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2016JointVentureMember_019c9bd2-c5c1-7eed-b275-73180cac8090" xlink:href="nsa-20260331.xsd#nsa_A2016JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019c9bd2-c5c1-70df-9c09-a4eba0944dab" xlink:to="loc_nsa_A2016JointVentureMember_019c9bd2-c5c1-7eed-b275-73180cac8090" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019d963d-0b40-7223-bc4c-1d944c263109" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c5c1-7b76-8415-dafdc37434d1" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019d963d-0b40-7223-bc4c-1d944c263109" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7223-bc4c-1d944c263109_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019d963d-0b40-7223-bc4c-1d944c263109" xlink:to="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7223-bc4c-1d944c263109_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019d963d-0b40-7223-bc4c-1d944c263109" xlink:to="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019d963d-0b40-7a36-9da5-4cc609ee3c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:to="loc_us-gaap_CommonStockMember_019d963d-0b40-7a36-9da5-4cc609ee3c9b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockMember_019ddf52-8d66-74f3-86fa-be984e7b6472" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:to="loc_us-gaap_PreferredStockMember_019ddf52-8d66-74f3-86fa-be984e7b6472" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_OPUnitMember_019db304-27ec-7c6a-beff-ecc198b4dd7d" xlink:href="nsa-20260331.xsd#nsa_OPUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:to="loc_nsa_OPUnitMember_019db304-27ec-7c6a-beff-ecc198b4dd7d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeriesA1CumulativeRedeemablePreferredUnitMember_019ddf53-ab75-7fa2-86a3-6301d331916a" xlink:href="nsa-20260331.xsd#nsa_SeriesA1CumulativeRedeemablePreferredUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:to="loc_nsa_SeriesA1CumulativeRedeemablePreferredUnitMember_019ddf53-ab75-7fa2-86a3-6301d331916a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LongTermIncentivePlanUnitMember_019ddf54-10a0-75d7-92cd-28bea3c0c906" xlink:href="nsa-20260331.xsd#nsa_LongTermIncentivePlanUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019d963d-0b40-7379-b4df-7a9c91f99fd5" xlink:to="loc_nsa_LongTermIncentivePlanUnitMember_019ddf54-10a0-75d7-92cd-28bea3c0c906" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfTopMetropolitanStatisticalAreasForFocusOfOperations_019dde16-d30b-79b9-b030-81ec4d89dba0" xlink:href="nsa-20260331.xsd#nsa_NumberOfTopMetropolitanStatisticalAreasForFocusOfOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_nsa_NumberOfTopMetropolitanStatisticalAreasForFocusOfOperations_019dde16-d30b-79b9-b030-81ec4d89dba0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_019dde16-d30b-7d49-8156-2ef311dbdac8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_019dde16-d30b-7d49-8156-2ef311dbdac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfStatesInWhichEntityOperates_019dde16-d30b-7308-a5c2-5851480e167c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfStatesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_NumberOfStatesInWhichEntityOperates_019dde16-d30b-7308-a5c2-5851480e167c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019dde16-d30b-7054-83d0-8e5a3aa5f50c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_NetRentableArea_019dde16-d30b-7054-83d0-8e5a3aa5f50c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfStorageUnits_019dde16-d30b-788e-b16f-eb1e5f114c32" xlink:href="nsa-20260331.xsd#nsa_NumberOfStorageUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_nsa_NumberOfStorageUnits_019dde16-d30b-788e-b16f-eb1e5f114c32" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019dde16-d30b-7886-91f9-ff9f83fba4de" xlink:href="nsa-20260331.xsd#nsa_NumberOfRealEstatePropertiesToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019dde16-d30b-7886-91f9-ff9f83fba4de" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019dde16-d30b-7799-83ef-5b01a35802ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfUnitsInRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019dde16-d30b-7799-83ef-5b01a35802ea" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dde16-d30b-7106-a200-7e13b238c1f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019dde16-d30b-7106-a200-7e13b238c1f8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesIssued1_019dde16-d30b-7b48-9a12-3274ee50807b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConversionOfStockSharesIssued1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_us-gaap_ConversionOfStockSharesIssued1_019dde16-d30b-7b48-9a12-3274ee50807b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ConversionOfStockNumberOfUnitsIssues_019ddf51-06f8-745b-8dc0-13a7f51cc1e0" xlink:href="nsa-20260331.xsd#nsa_ConversionOfStockNumberOfUnitsIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c5c1-7db9-bf4d-93e3659fd718" xlink:to="loc_nsa_ConversionOfStockNumberOfUnitsIssues_019ddf51-06f8-745b-8dc0-13a7f51cc1e0" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SUMMARYOFSIGNIFICANTACCOUNTINGPOLICIESDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfVariableInterestEntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019c9bd2-c5c1-7df2-8f1c-8f282661ba23" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019c9bd2-c5c1-7df2-8f1c-8f282661ba23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c9bd2-c5c1-7df2-8f1c-8f282661ba23_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c9bd2-c5c1-7df2-8f1c-8f282661ba23" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c9bd2-c5c1-7df2-8f1c-8f282661ba23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019c9bd2-c5c1-79d2-83fd-f80e9837bd08" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019c9bd2-c5c1-7df2-8f1c-8f282661ba23" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019c9bd2-c5c1-79d2-83fd-f80e9837bd08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c9bd2-c5c1-7249-8619-ca4440372014" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019c9bd2-c5c1-79d2-83fd-f80e9837bd08" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_019c9bd2-c5c1-7249-8619-ca4440372014" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c5c1-77d6-a9be-d822cb422419" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c5c1-77d6-a9be-d822cb422419" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c5c1-77d6-a9be-d822cb422419_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c5c1-77d6-a9be-d822cb422419" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c5c1-77d6-a9be-d822cb422419_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c5c1-71c4-b563-17ad11dfcdfb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c5c1-77d6-a9be-d822cb422419" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c5c1-71c4-b563-17ad11dfcdfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FixedRateMortgagesMember_019c9bd2-c5c1-7de5-b056-960c5f1fd1bd" xlink:href="nsa-20260331.xsd#nsa_FixedRateMortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c5c1-71c4-b563-17ad11dfcdfb" xlink:to="loc_nsa_FixedRateMortgagesMember_019c9bd2-c5c1-7de5-b056-960c5f1fd1bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c5c1-7fb4-961e-d005c50aae95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c5c1-7fb4-961e-d005c50aae95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c5c1-7fb4-961e-d005c50aae95_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c5c1-7fb4-961e-d005c50aae95" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c5c1-7fb4-961e-d005c50aae95_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c5c1-7853-963d-49dcc137b065" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c5c1-7fb4-961e-d005c50aae95" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c5c1-7853-963d-49dcc137b065" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesMember_019c9bd2-c5c1-7a07-a5d1-6129c2d1dab8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c5c1-7853-963d-49dcc137b065" xlink:to="loc_us-gaap_MortgagesMember_019c9bd2-c5c1-7a07-a5d1-6129c2d1dab8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c5c1-7c54-b5a7-8aa68ad5f6ec" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TenantInsuranceAndProtectionPlanFeesAndCommissionsMember_019c9bd2-c5c1-7ded-b342-c2f3d64ad8bc" xlink:href="nsa-20260331.xsd#nsa_TenantInsuranceAndProtectionPlanFeesAndCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:to="loc_nsa_TenantInsuranceAndProtectionPlanFeesAndCommissionsMember_019c9bd2-c5c1-7ded-b342-c2f3d64ad8bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_RetailProductsAndSuppliesMember_019c9bd2-c5c1-77ef-95cc-d8634d085f97" xlink:href="nsa-20260331.xsd#nsa_RetailProductsAndSuppliesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:to="loc_nsa_RetailProductsAndSuppliesMember_019c9bd2-c5c1-77ef-95cc-d8634d085f97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PropertyManagementCallCenterAndPlatformFeesMember_019c9bd2-c5c1-7763-b057-a45a1cfa5ef7" xlink:href="nsa-20260331.xsd#nsa_PropertyManagementCallCenterAndPlatformFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:to="loc_nsa_PropertyManagementCallCenterAndPlatformFeesMember_019c9bd2-c5c1-7763-b057-a45a1cfa5ef7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TenantWarrantyProtectionMember_019c9bd2-c5c1-7fe1-a050-0329b716734e" xlink:href="nsa-20260331.xsd#nsa_TenantWarrantyProtectionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c5c1-7efc-a49d-fad8e8c89eed" xlink:to="loc_nsa_TenantWarrantyProtectionMember_019c9bd2-c5c1-7fe1-a050-0329b716734e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019de237-bc6e-7b11-932e-c7dacc4aa1e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019de237-bc6e-7d91-9eb3-7c0b2aaad2f2" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019de237-bc6e-7b11-932e-c7dacc4aa1e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019de237-bc6e-7f5b-8167-cbca38155921" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019de237-bc6e-7b11-932e-c7dacc4aa1e2" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019de237-bc6e-7f5b-8167-cbca38155921" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019de237-bc6e-7604-ab88-75c3f641ce2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfVariableInterestEntitiesTable_019c9bd2-c5c1-7606-8ca8-9c8acc74d48d" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019de237-bc6e-7604-ab88-75c3f641ce2b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019de237-bc6e-7604-ab88-75c3f641ce2b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019de237-bc6e-7604-ab88-75c3f641ce2b" xlink:to="loc_us-gaap_RelatedPartyDomain_019de237-bc6e-7604-ab88-75c3f641ce2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019de237-bc6e-752e-b255-6db6abcfddb6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019de237-bc6e-7604-ab88-75c3f641ce2b" xlink:to="loc_us-gaap_RelatedPartyDomain_019de237-bc6e-752e-b255-6db6abcfddb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ThirdPartyMember_019de237-bc6e-7ed3-91c3-b990c5a3b45b" xlink:href="nsa-20260331.xsd#nsa_ThirdPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019de237-bc6e-752e-b255-6db6abcfddb6" xlink:to="loc_nsa_ThirdPartyMember_019de237-bc6e-7ed3-91c3-b990c5a3b45b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfPartnershipsConsideredVariableInterestEntities_019c9bd2-c5c1-74c9-b60c-6c11ca00f4e4" xlink:href="nsa-20260331.xsd#nsa_NumberOfPartnershipsConsideredVariableInterestEntities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_NumberOfPartnershipsConsideredVariableInterestEntities_019c9bd2-c5c1-74c9-b60c-6c11ca00f4e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_019c9bd2-c5c1-7579-a86c-2d09ed75afd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_019c9bd2-c5c1-7579-a86c-2d09ed75afd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019c9bd2-c5c1-77d7-8678-f4647d2c9e60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019c9bd2-c5c1-77d7-8678-f4647d2c9e60" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_DebtLongTermAndShortTermCombinedAmountsGross_019c9bd2-c5c1-720d-9007-91c3ab2f1762" xlink:href="nsa-20260331.xsd#nsa_DebtLongTermAndShortTermCombinedAmountsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_DebtLongTermAndShortTermCombinedAmountsGross_019c9bd2-c5c1-720d-9007-91c3ab2f1762" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup_019de237-bc6e-7668-80b6-9369f067dc7c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_us-gaap_AssetsHeldForSaleNotPartOfDisposalGroup_019de237-bc6e-7668-80b6-9369f067dc7c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019de237-bc6e-7108-b0eb-8f2e8b40a7fc" xlink:href="nsa-20260331.xsd#nsa_NumberOfRealEstatePropertiesToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019de237-bc6e-7108-b0eb-8f2e8b40a7fc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c5c1-7acc-9748-33eeec01a8a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c5c1-7acc-9748-33eeec01a8a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PropertyManagementFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets_019c9bd2-c5c1-7cf1-938c-d7856adf4ed5" xlink:href="nsa-20260331.xsd#nsa_PropertyManagementFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_PropertyManagementFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets_019c9bd2-c5c1-7cf1-938c-d7856adf4ed5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PlatformFeesPerJointVenturePropertyPerMonth_019c9bd2-c5c1-76ad-b25c-3a18e6a56fe5" xlink:href="nsa-20260331.xsd#nsa_PlatformFeesPerJointVenturePropertyPerMonth"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_PlatformFeesPerJointVenturePropertyPerMonth_019c9bd2-c5c1-76ad-b25c-3a18e6a56fe5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_CallCenterFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets_019c9bd2-c5c1-7e59-b409-47f0c1c124f9" xlink:href="nsa-20260331.xsd#nsa_CallCenterFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_CallCenterFeesPercentOfMonthlyGrossRevenuesAndNetSalesRevenueOfJointVentureAssets_019c9bd2-c5c1-7e59-b409-47f0c1c124f9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TenantWarrantyPlanProceedsPerPropertyPercent_019c9bd2-c5c1-7340-b821-4f073f08d910" xlink:href="nsa-20260331.xsd#nsa_TenantWarrantyPlanProceedsPerPropertyPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableInterestEntityLineItems_019c9bd2-c5c1-7c38-9426-dec03efc1c8c" xlink:to="loc_nsa_TenantWarrantyPlanProceedsPerPropertyPercent_019c9bd2-c5c1-7340-b821-4f073f08d910" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c66d-7c3a-9b1d-b275654e97c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c66d-7c3a-9b1d-b275654e97c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-7c3a-9b1d-b275654e97c9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c66d-7c3a-9b1d-b275654e97c9" xlink:to="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-7c3a-9b1d-b275654e97c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-78d5-90e9-076e9df14f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019c9bd2-c66d-7c3a-9b1d-b275654e97c9" xlink:to="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-78d5-90e9-076e9df14f1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemablePreferredStockMember_019c9bd2-c66d-7466-88d8-18415ec0d35d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RedeemablePreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-78d5-90e9-076e9df14f1c" xlink:to="loc_us-gaap_RedeemablePreferredStockMember_019c9bd2-c66d-7466-88d8-18415ec0d35d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019c9bd2-c66d-70a3-8a75-d6adfd682650" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019c9bd2-c66d-78d5-90e9-076e9df14f1c" xlink:to="loc_us-gaap_CommonClassAMember_019c9bd2-c66d-70a3-8a75-d6adfd682650" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019c9bd2-c66d-7364-998c-79004d2bfd28" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_dei_LegalEntityAxis_019c9bd2-c66d-7364-998c-79004d2bfd28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-7364-998c-79004d2bfd28_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-7364-998c-79004d2bfd28" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-7364-998c-79004d2bfd28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-7be4-b64f-8ffa00d1ecda" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-7364-998c-79004d2bfd28" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-7be4-b64f-8ffa00d1ecda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NSAOPLPMember_019c9bd2-c66d-7d43-bd21-836697e358d3" xlink:href="nsa-20260331.xsd#nsa_NSAOPLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c9bd2-c66d-7be4-b64f-8ffa00d1ecda" xlink:to="loc_nsa_NSAOPLPMember_019c9bd2-c66d-7d43-bd21-836697e358d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-764c-96ea-29a9d9c9820b" xlink:href="nsa-20260331.xsd#nsa_DownREITPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c9bd2-c66d-7be4-b64f-8ffa00d1ecda" xlink:to="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-764c-96ea-29a9d9c9820b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7ebc-845f-eb52165b16c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7ebc-845f-eb52165b16c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7ebc-845f-eb52165b16c4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7ebc-845f-eb52165b16c4" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7ebc-845f-eb52165b16c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7ebc-845f-eb52165b16c4" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_019c9bd2-c66d-73fd-8753-ab426e7845dd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeriesAPreferredStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_019c9bd2-c66d-73fd-8753-ab426e7845dd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeriesA1PreferredUnitsMember_019c9bd2-c66d-7089-8360-13bf32d0b859" xlink:href="nsa-20260331.xsd#nsa_SeriesA1PreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:to="loc_nsa_SeriesA1PreferredUnitsMember_019c9bd2-c66d-7089-8360-13bf32d0b859" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7f4a-b140-a630cf24b48a" xlink:href="nsa-20260331.xsd#nsa_ClassAUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:to="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7f4a-b140-a630cf24b48a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7316-8909-e6e39b39004d" xlink:href="nsa-20260331.xsd#nsa_LongTermIncentivePlanUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:to="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7316-8909-e6e39b39004d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ClassBUnitMember_019c9bd2-c66d-7e58-910f-3e21feab8047" xlink:href="nsa-20260331.xsd#nsa_ClassBUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7450-9684-7a86a4953648" xlink:to="loc_nsa_ClassBUnitMember_019c9bd2-c66d-7e58-910f-3e21feab8047" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_019c9bd2-c66d-77ef-aede-31915b81c6c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_019c9bd2-c66d-77ef-aede-31915b81c6c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-77ef-aede-31915b81c6c9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019c9bd2-c66d-77ef-aede-31915b81c6c9" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-77ef-aede-31915b81c6c9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-7e1f-b12b-11de6bc399ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_019c9bd2-c66d-77ef-aede-31915b81c6c9" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-7e1f-b12b-11de6bc399ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PriorAtTheMarketSalesAgreementMember_019c9bd2-c66d-7c23-86c9-461506b60e9e" xlink:href="nsa-20260331.xsd#nsa_PriorAtTheMarketSalesAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-7e1f-b12b-11de6bc399ac" xlink:to="loc_nsa_PriorAtTheMarketSalesAgreementMember_019c9bd2-c66d-7c23-86c9-461506b60e9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_AtTheMarketProgramMember_019c9bd2-c66d-74da-9447-bde8f3c224f5" xlink:href="nsa-20260331.xsd#nsa_AtTheMarketProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_019c9bd2-c66d-7e1f-b12b-11de6bc399ac" xlink:to="loc_nsa_AtTheMarketProgramMember_019c9bd2-c66d-74da-9447-bde8f3c224f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c66d-7755-ab91-4a8d3e425ab5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c66d-7755-ab91-4a8d3e425ab5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9bd2-c66d-7755-ab91-4a8d3e425ab5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c66d-7755-ab91-4a8d3e425ab5" xlink:to="loc_us-gaap_EquityComponentDomain_019c9bd2-c66d-7755-ab91-4a8d3e425ab5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019c9bd2-c66d-7ca7-a4d4-313ddc4b5084" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019c9bd2-c66d-7755-ab91-4a8d3e425ab5" xlink:to="loc_us-gaap_EquityComponentDomain_019c9bd2-c66d-7ca7-a4d4-313ddc4b5084" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019c9bd2-c66d-7cf7-ac7f-744b0e88c35f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019c9bd2-c66d-7ca7-a4d4-313ddc4b5084" xlink:to="loc_us-gaap_CommonStockMember_019c9bd2-c66d-7cf7-ac7f-744b0e88c35f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionAxis_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019c9bd2-c66d-7358-aea4-e119bbd94997" xlink:to="loc_us-gaap_AssetAcquisitionAxis_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AssetAcquisitionAxis_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7" xlink:to="loc_us-gaap_AssetAcquisitionDomain_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionDomain_019c9bd2-c66d-7a94-9fd9-74161cb42e07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AssetAcquisitionAxis_019c9bd2-c66d-7d49-9e6f-eb854ebef5e7" xlink:to="loc_us-gaap_AssetAcquisitionDomain_019c9bd2-c66d-7a94-9fd9-74161cb42e07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_RetirementOfNorthwestMember_019c9bd2-c66d-7cd4-920a-3518fb307835" xlink:href="nsa-20260331.xsd#nsa_RetirementOfNorthwestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionDomain_019c9bd2-c66d-7a94-9fd9-74161cb42e07" xlink:to="loc_nsa_RetirementOfNorthwestMember_019c9bd2-c66d-7cd4-920a-3518fb307835" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_019c9bd2-c66d-7bd6-9d22-d3269ab45eb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockDividendRatePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_019c9bd2-c66d-7bd6-9d22-d3269ab45eb4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockPerShareAmountsOfPreferredDividendsInArrears_019c9bd2-c66d-7002-87c4-90a1554ecc98" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockPerShareAmountsOfPreferredDividendsInArrears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_PreferredStockPerShareAmountsOfPreferredDividendsInArrears_019c9bd2-c66d-7002-87c4-90a1554ecc98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockRedemptionPricePerShare_019c9bd2-c66d-7146-94d7-03c8a38bf508" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockRedemptionPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_PreferredStockRedemptionPricePerShare_019c9bd2-c66d-7146-94d7-03c8a38bf508" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019c9bd2-c66d-7771-9531-887c51257c95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019c9bd2-c66d-7771-9531-887c51257c95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_019c9bd2-c66d-76c4-80a9-fbb6c9175cb2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_019c9bd2-c66d-76c4-80a9-fbb6c9175cb2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_CommonAndPreferredStockValueOfSharesAuthorizedUnderATMProgram_019c9bd2-c66d-7147-9223-63abc66dcee5" xlink:href="nsa-20260331.xsd#nsa_CommonAndPreferredStockValueOfSharesAuthorizedUnderATMProgram"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_nsa_CommonAndPreferredStockValueOfSharesAuthorizedUnderATMProgram_019c9bd2-c66d-7147-9223-63abc66dcee5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_019c9bd2-c66d-7350-a66e-803b02e5678d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_019c9bd2-c66d-7350-a66e-803b02e5678d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_CommonAndPreferredStockRemainingValueOfSharesAuthorizedUnderATMProgram_019c9bd2-c66d-7a75-b792-2c53b72ea5a4" xlink:href="nsa-20260331.xsd#nsa_CommonAndPreferredStockRemainingValueOfSharesAuthorizedUnderATMProgram"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_nsa_CommonAndPreferredStockRemainingValueOfSharesAuthorizedUnderATMProgram_019c9bd2-c66d-7a75-b792-2c53b72ea5a4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019c9bd2-c66d-7996-a1f7-54dabfa8c843" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_019c9bd2-c66d-7996-a1f7-54dabfa8c843" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019c9bd2-c66d-7e23-a8ac-61d6a79a7fd8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019c9bd2-c66d-7e23-a8ac-61d6a79a7fd8" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_EquityInstrumentConvertibleConversionRatio_019c9bd2-c66d-74b8-8d6e-3089b2e9308c" xlink:href="nsa-20260331.xsd#nsa_EquityInstrumentConvertibleConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_nsa_EquityInstrumentConvertibleConversionRatio_019c9bd2-c66d-74b8-8d6e-3089b2e9308c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_StockholdersEquityNoteUnitConversionMinimumConversionPeriod_019c9bd2-c66d-71fe-b040-6d33c3bf5a50" xlink:href="nsa-20260331.xsd#nsa_StockholdersEquityNoteUnitConversionMinimumConversionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_nsa_StockholdersEquityNoteUnitConversionMinimumConversionPeriod_019c9bd2-c66d-71fe-b040-6d33c3bf5a50" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConversionOfStockSharesConverted1_019c9bd2-c66d-7dd3-b243-9e98b940cda9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConversionOfStockSharesConverted1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_ConversionOfStockSharesConverted1_019c9bd2-c66d-7dd3-b243-9e98b940cda9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019c9bd2-c66d-78e2-b984-6f8c3f4b49a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019c9bd2-c66d-7049-94df-6a3f35aa4c7a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019c9bd2-c66d-78e2-b984-6f8c3f4b49a8" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSScheduleofUnitsReflectingNoncontrollingInterestsDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSScheduleofUnitsReflectingNoncontrollingInterestsDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SHAREHOLDERSEQUITYANDNONCONTROLLINGINTERESTSScheduleofUnitsReflectingNoncontrollingInterestsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_019c9bd2-c66d-70b8-98a8-93ab3d255695" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_019c9bd2-c66d-70f8-b6ef-01085b556ec7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_019c9bd2-c66d-70b8-98a8-93ab3d255695" xlink:to="loc_us-gaap_MinorityInterestTable_019c9bd2-c66d-70f8-b6ef-01085b556ec7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7a56-87e1-385482c97c41" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_019c9bd2-c66d-70f8-b6ef-01085b556ec7" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7a56-87e1-385482c97c41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7a56-87e1-385482c97c41_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7a56-87e1-385482c97c41" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7a56-87e1-385482c97c41_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7743-bde2-0dd7e0b97cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7a56-87e1-385482c97c41" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7743-bde2-0dd7e0b97cc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeriesA1PreferredUnitsMember_019c9bd2-c66d-745e-8a50-ec83c0a55b9a" xlink:href="nsa-20260331.xsd#nsa_SeriesA1PreferredUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7743-bde2-0dd7e0b97cc0" xlink:to="loc_nsa_SeriesA1PreferredUnitsMember_019c9bd2-c66d-745e-8a50-ec83c0a55b9a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7eec-a5f7-15d44627f953" xlink:href="nsa-20260331.xsd#nsa_ClassAUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7743-bde2-0dd7e0b97cc0" xlink:to="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7eec-a5f7-15d44627f953" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7822-98c5-96a1650fa47e" xlink:href="nsa-20260331.xsd#nsa_LongTermIncentivePlanUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7743-bde2-0dd7e0b97cc0" xlink:to="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7822-98c5-96a1650fa47e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019c9bd2-c66d-7a9f-a529-dc2d82740f26" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_019c9bd2-c66d-70f8-b6ef-01085b556ec7" xlink:to="loc_dei_LegalEntityAxis_019c9bd2-c66d-7a9f-a529-dc2d82740f26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-7a9f-a529-dc2d82740f26_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-7a9f-a529-dc2d82740f26" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-7a9f-a529-dc2d82740f26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-703f-bba2-76b6d6d66f1e" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-7a9f-a529-dc2d82740f26" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-703f-bba2-76b6d6d66f1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PartnershipSubsidiariesMember_019c9bd2-c66d-7255-a1fc-554c0a366d5f" xlink:href="nsa-20260331.xsd#nsa_PartnershipSubsidiariesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c9bd2-c66d-703f-bba2-76b6d6d66f1e" xlink:to="loc_nsa_PartnershipSubsidiariesMember_019c9bd2-c66d-7255-a1fc-554c0a366d5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NSAOPLPMember_019c9bd2-c66d-7146-b024-77669217ca94" xlink:href="nsa-20260331.xsd#nsa_NSAOPLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nsa_PartnershipSubsidiariesMember_019c9bd2-c66d-7255-a1fc-554c0a366d5f" xlink:to="loc_nsa_NSAOPLPMember_019c9bd2-c66d-7146-b024-77669217ca94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-7f50-b4f7-e5262256dd66" xlink:href="nsa-20260331.xsd#nsa_DownREITPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nsa_PartnershipSubsidiariesMember_019c9bd2-c66d-7255-a1fc-554c0a366d5f" xlink:to="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-7f50-b4f7-e5262256dd66" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019c9bd2-c66d-73d6-9d53-361d10c6af06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_019c9bd2-c66d-70b8-98a8-93ab3d255695" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019c9bd2-c66d-73d6-9d53-361d10c6af06" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c66d-7697-8d91-3420a8792635" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c66d-7697-8d91-3420a8792635" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019d686a-efde-7a5c-b223-2a5c190e8608" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c66d-7697-8d91-3420a8792635" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019d686a-efde-7a5c-b223-2a5c190e8608" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7a5c-b223-2a5c190e8608_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019d686a-efde-7a5c-b223-2a5c190e8608" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7a5c-b223-2a5c190e8608_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_019d686a-efde-7a5c-b223-2a5c190e8608" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2018JointVentureMember_019d686a-efde-7d85-8bcf-6bcbb4a30132" xlink:href="nsa-20260331.xsd#nsa_A2018JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:to="loc_nsa_A2018JointVentureMember_019d686a-efde-7d85-8bcf-6bcbb4a30132" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2024JointVentureMember_019d686a-efde-73df-8094-54f6cee554ac" xlink:href="nsa-20260331.xsd#nsa_A2024JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:to="loc_nsa_A2024JointVentureMember_019d686a-efde-73df-8094-54f6cee554ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2023JointVentureMember_019d686a-efde-750e-91a7-7445388876ec" xlink:href="nsa-20260331.xsd#nsa_A2023JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:to="loc_nsa_A2023JointVentureMember_019d686a-efde-750e-91a7-7445388876ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2016JointVentureMember_019d686a-efde-710c-9cd5-ccfe8799c07c" xlink:href="nsa-20260331.xsd#nsa_A2016JointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_019d686a-efde-7cfc-ae1b-27e8cf303b7a" xlink:to="loc_nsa_A2016JointVentureMember_019d686a-efde-710c-9cd5-ccfe8799c07c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesAxis_019d686a-efde-7d68-8599-7dbe66d7cb65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c66d-7697-8d91-3420a8792635" xlink:to="loc_us-gaap_RealEstatePropertiesAxis_019d686a-efde-7d68-8599-7dbe66d7cb65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019d686a-efde-7d68-8599-7dbe66d7cb65_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019d686a-efde-7d68-8599-7dbe66d7cb65" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019d686a-efde-7d68-8599-7dbe66d7cb65_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstatePropertiesDomain_019d686a-efde-7ee1-909a-d401b92ced05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstatePropertiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RealEstatePropertiesAxis_019d686a-efde-7d68-8599-7dbe66d7cb65" xlink:to="loc_us-gaap_RealEstatePropertiesDomain_019d686a-efde-7ee1-909a-d401b92ced05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnconsolidatedPropertiesMember_019d686a-efde-7cdc-a3c6-b5440bd87bee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnconsolidatedPropertiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RealEstatePropertiesDomain_019d686a-efde-7ee1-909a-d401b92ced05" xlink:to="loc_us-gaap_UnconsolidatedPropertiesMember_019d686a-efde-7cdc-a3c6-b5440bd87bee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019d686a-efde-724c-ab02-b45ff756b079" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_019c9bd2-c66d-7697-8d91-3420a8792635" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019d686a-efde-724c-ab02-b45ff756b079" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019d686a-efde-724c-ab02-b45ff756b079_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019d686a-efde-724c-ab02-b45ff756b079" xlink:to="loc_us-gaap_RelatedPartyDomain_019d686a-efde-724c-ab02-b45ff756b079_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019d686a-efde-7b4e-b0dc-40abdaf88a33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019d686a-efde-724c-ab02-b45ff756b079" xlink:to="loc_us-gaap_RelatedPartyDomain_019d686a-efde-7b4e-b0dc-40abdaf88a33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateJointVentureMember_019d686a-efde-7fe3-a380-6babfd99f134" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019d686a-efde-7b4e-b0dc-40abdaf88a33" xlink:to="loc_us-gaap_CorporateJointVentureMember_019d686a-efde-7fe3-a380-6babfd99f134" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019d686a-efde-77dd-b2a3-240ca10d21ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_019d686a-efde-77dd-b2a3-240ca10d21ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfRealEstateProperties_019d686a-efde-73a9-b326-e6e4f83ffaa1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfRealEstateProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_NumberOfRealEstateProperties_019d686a-efde-73a9-b326-e6e4f83ffaa1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019d686a-efde-74c1-a661-dfaa1af08739" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_NetRentableArea_019d686a-efde-74c1-a661-dfaa1af08739" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfStorageUnits_019d686a-efde-7df0-9a06-351984875760" xlink:href="nsa-20260331.xsd#nsa_NumberOfStorageUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_nsa_NumberOfStorageUnits_019d686a-efde-7df0-9a06-351984875760" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfStatesInWhichEntityOperates_019d686a-efde-7527-88b2-7e21b4908ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfStatesInWhichEntityOperates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_NumberOfStatesInWhichEntityOperates_019d686a-efde-7527-88b2-7e21b4908ab7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019d686a-efde-772a-8f73-91446514f715" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfUnitsInRealEstateProperty"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_019c9bd2-c66d-7602-badd-77e15fa2d827" xlink:to="loc_us-gaap_NumberOfUnitsInRealEstateProperty_019d686a-efde-772a-8f73-91446514f715" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedFinancialPositionDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedFinancialPositionDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedFinancialPositionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-7f60-b248-08357ba3b8ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7edb-8c0f-101f76ac6969" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-7f60-b248-08357ba3b8ea" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7edb-8c0f-101f76ac6969" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7559-87bc-bc2dd481f685" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7edb-8c0f-101f76ac6969" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7559-87bc-bc2dd481f685" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7559-87bc-bc2dd481f685_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7559-87bc-bc2dd481f685" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7559-87bc-bc2dd481f685_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-750a-a334-a5787aa8fa2b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7559-87bc-bc2dd481f685" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-750a-a334-a5787aa8fa2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c66d-7afc-a0b5-ddd09137ce95" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-750a-a334-a5787aa8fa2b" xlink:to="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c66d-7afc-a0b5-ddd09137ce95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7edb-8c0f-101f76ac6969" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7553-8d8f-f3d41f5520e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7f64-a1d6-7c3cf8ee3637" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7553-8d8f-f3d41f5520e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_019c9bd2-c66d-7b75-ad18-eadcf14ea5cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7553-8d8f-f3d41f5520e4" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_019c9bd2-c66d-7b75-ad18-eadcf14ea5cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract_019c9bd2-c66d-75b1-bacc-59631e023875" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-7f60-b248-08357ba3b8ea" xlink:to="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract_019c9bd2-c66d-75b1-bacc-59631e023875" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract_019c9bd2-c66d-75b1-bacc-59631e023875" xlink:to="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019c9bd2-c66d-7ddc-9d10-76e71f969045" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateInvestmentPropertyAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAtCost_019c9bd2-c66d-7ddc-9d10-76e71f969045" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019c9bd2-c66d-7e50-a756-8166b181938b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyAccumulatedDepreciation_019c9bd2-c66d-7e50-a756-8166b181938b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateInvestmentPropertyNet_019c9bd2-c66d-7c8e-823f-4a3c924c5285" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateInvestmentPropertyNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:to="loc_us-gaap_RealEstateInvestmentPropertyNet_019c9bd2-c66d-7c8e-823f-4a3c924c5285" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019c9bd2-c66d-7eea-a5bd-fa4e2ba700b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:to="loc_us-gaap_OtherAssets_019c9bd2-c66d-7eea-a5bd-fa4e2ba700b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019c9bd2-c66d-7a6f-acc6-aad9adc9941d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019c9bd2-c66d-775d-b1cc-21c991292b4c" xlink:to="loc_us-gaap_Assets_019c9bd2-c66d-7a6f-acc6-aad9adc9941d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAbstract_019c9bd2-c66d-75b1-bacc-59631e023875" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_019c9bd2-c66d-7ec5-a0cf-4dd3d6a5f1df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_019c9bd2-c66d-7ec5-a0cf-4dd3d6a5f1df" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_019c9bd2-c66d-7d35-a6bb-e23e9e76cae1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:to="loc_us-gaap_OtherLiabilities_019c9bd2-c66d-7d35-a6bb-e23e9e76cae1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019c9bd2-c66d-7c90-b9af-da7703026aab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019c9bd2-c66d-7c90-b9af-da7703026aab" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019c9bd2-c66d-78c8-a522-66cf8a69cdac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019c9bd2-c66d-7e24-a0d1-af7586a0c863" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019c9bd2-c66d-78c8-a522-66cf8a69cdac" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedOperatingInformationDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedOperatingInformationDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/INVESTMENTINUNCONSOLIDATEDREALESTATEVENTURESScheduleofCondensedOperatingInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7733-ba81-3c42f6ee0ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7733-ba81-3c42f6ee0ed6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7733-ba81-3c42f6ee0ed6" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7548-ba00-52f6e5dd5760" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7ab6-b210-ca2bfa649d6a" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7548-ba00-52f6e5dd5760" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c66d-776b-9724-7bcbb8c336b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7548-ba00-52f6e5dd5760" xlink:to="loc_us-gaap_CorporateJointVentureMember_019c9bd2-c66d-776b-9724-7bcbb8c336b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7feb-9432-5a2038a9ce28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019c9bd2-c66d-7733-ba81-3c42f6ee0ed6" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7feb-9432-5a2038a9ce28" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7feb-9432-5a2038a9ce28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7feb-9432-5a2038a9ce28" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7feb-9432-5a2038a9ce28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7ee6-a47f-0663136af29d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_019c9bd2-c66d-7feb-9432-5a2038a9ce28" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7ee6-a47f-0663136af29d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_019c9bd2-c66d-7165-9fa2-2b4cfd863d32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_019c9bd2-c66d-7ee6-a47f-0663136af29d" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesMember_019c9bd2-c66d-7165-9fa2-2b4cfd863d32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019c9bd2-c66d-7141-8e10-d61bb4034af7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_Revenues_019c9bd2-c66d-7141-8e10-d61bb4034af7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_019c9bd2-c66d-7fd8-aeca-279a6f71d124" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_CostOfRevenue_019c9bd2-c66d-7fd8-aeca-279a6f71d124" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019c9bd2-c66d-74c3-8cf1-f44d3a586f96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_019c9bd2-c66d-74c3-8cf1-f44d3a586f96" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c66d-732e-b028-e90aa32de941" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c66d-732e-b028-e90aa32de941" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c66d-736d-9dc8-f576fb3927df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c66d-736d-9dc8-f576fb3927df" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c66d-7976-a8ea-48acab4d1287" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c66d-7976-a8ea-48acab4d1287" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019c9bd2-c66d-7721-9ca4-1ab3823b9e46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019c9bd2-c66d-74cc-8d68-c1a3559ad4fb" xlink:to="loc_us-gaap_NetIncomeLoss_019c9bd2-c66d-7721-9ca4-1ab3823b9e46" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/ACQUISITIONSANDDISPOSITIONSNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#ACQUISITIONSANDDISPOSITIONSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/ACQUISITIONSANDDISPOSITIONSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetAcquisitionTable_019c9bd2-c66d-7167-9ef6-c3055cf9140a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_us-gaap_AssetAcquisitionTable_019c9bd2-c66d-7167-9ef6-c3055cf9140a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7405-91a7-1757a062d7a7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_019c9bd2-c66d-7167-9ef6-c3055cf9140a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7405-91a7-1757a062d7a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7405-91a7-1757a062d7a7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7405-91a7-1757a062d7a7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7405-91a7-1757a062d7a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7ba9-800f-a60c938bf08b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7405-91a7-1757a062d7a7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7ba9-800f-a60c938bf08b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-7b08-b369-b3586f9bbec2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeasesAcquiredInPlaceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7ba9-800f-a60c938bf08b" xlink:to="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-7b08-b369-b3586f9bbec2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7a07-bfbd-81ef7be5677d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_019c9bd2-c66d-7167-9ef6-c3055cf9140a" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7a07-bfbd-81ef7be5677d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7a07-bfbd-81ef7be5677d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7a07-bfbd-81ef7be5677d" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7a07-bfbd-81ef7be5677d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7c06-b6c1-7ab9e5001ea5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-7a07-bfbd-81ef7be5677d" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7c06-b6c1-7ab9e5001ea5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ThirdPartyMember_019c9bd2-c66d-7da4-a8c2-52113f5e5f60" xlink:href="nsa-20260331.xsd#nsa_ThirdPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7c06-b6c1-7ab9e5001ea5" xlink:to="loc_nsa_ThirdPartyMember_019c9bd2-c66d-7da4-a8c2-52113f5e5f60" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019d962e-7c85-761b-ab20-5986e8c778c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AssetAcquisitionTable_019c9bd2-c66d-7167-9ef6-c3055cf9140a" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019d962e-7c85-761b-ab20-5986e8c778c8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019d962e-7c85-761b-ab20-5986e8c778c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019d962e-7c85-761b-ab20-5986e8c778c8" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019d962e-7c85-761b-ab20-5986e8c778c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019d962e-7c86-766b-acf7-86384cdfb155" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019d962e-7c85-761b-ab20-5986e8c778c8" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019d962e-7c86-766b-acf7-86384cdfb155" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019d962e-7c86-7959-ad3c-d391b09e352e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019d962e-7c86-766b-acf7-86384cdfb155" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019d962e-7c86-7959-ad3c-d391b09e352e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfAssetsAcquiredProperties_019c9bd2-c66d-7cd6-b698-ba6c71e8d338" xlink:href="nsa-20260331.xsd#nsa_NumberOfAssetsAcquiredProperties"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_nsa_NumberOfAssetsAcquiredProperties_019c9bd2-c66d-7cd6-b698-ba6c71e8d338" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_AssetAcquisitionAssetsAcquiredandLiabilitiesAssumedNet_019c9bd2-c66d-722f-9b21-ec89105779ec" xlink:href="nsa-20260331.xsd#nsa_AssetAcquisitionAssetsAcquiredandLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_nsa_AssetAcquisitionAssetsAcquiredandLiabilitiesAssumedNet_019c9bd2-c66d-722f-9b21-ec89105779ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_019c9bd2-c66d-7bc4-a8bf-6747a2b811af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_us-gaap_FinitelivedIntangibleAssetsAcquired1_019c9bd2-c66d-7bc4-a8bf-6747a2b811af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsPeriodIncreaseDecrease_019db2fe-e21f-7f91-adb6-15884393ad3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsPeriodIncreaseDecrease_019db2fe-e21f-7f91-adb6-15884393ad3f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfSelfStoragePropertiesDisposition_019c9bd2-c66d-78ae-b6f6-818fcabd85bd" xlink:href="nsa-20260331.xsd#nsa_NumberOfSelfStoragePropertiesDisposition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_nsa_NumberOfSelfStoragePropertiesDisposition_019c9bd2-c66d-78ae-b6f6-818fcabd85bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyHeldForSale_019c9bd2-c66d-7891-8563-41beab17ca74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfPropertyHeldForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyHeldForSale_019c9bd2-c66d-7891-8563-41beab17ca74" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019c9bd2-c66d-7753-b838-151c05c4b446" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_019c9bd2-c66d-7753-b838-151c05c4b446" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019d962e-7c86-761d-99ee-3356a325decc" xlink:href="nsa-20260331.xsd#nsa_NumberOfRealEstatePropertiesToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetAcquisitionLineItems_019c9bd2-c66d-777c-a849-a7f66667adde" xlink:to="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019d962e-7c86-761d-99ee-3356a325decc" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/OTHERASSETSScheduleofOtherAssetsDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#OTHERASSETSScheduleofOtherAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/OTHERASSETSScheduleofOtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7211-bf32-3115dd589e15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-7b10-93bb-88adf4a2216c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7211-bf32-3115dd589e15" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-7b10-93bb-88adf4a2216c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-72ff-8893-9b24085b59f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-7b10-93bb-88adf4a2216c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-72ff-8893-9b24085b59f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-72ff-8893-9b24085b59f5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-72ff-8893-9b24085b59f5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-72ff-8893-9b24085b59f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7318-b2e5-deb9374e34a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-72ff-8893-9b24085b59f5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7318-b2e5-deb9374e34a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_019c9bd2-c66d-7838-8356-75068543bc82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7318-b2e5-deb9374e34a1" xlink:to="loc_us-gaap_TradeNamesMember_019c9bd2-c66d-7838-8356-75068543bc82" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-705d-96b6-262d1a19b4f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-7b10-93bb-88adf4a2216c" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-705d-96b6-262d1a19b4f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-705d-96b6-262d1a19b4f1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-705d-96b6-262d1a19b4f1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-705d-96b6-262d1a19b4f1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-792a-addb-21e70dee548f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-705d-96b6-262d1a19b4f1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-792a-addb-21e70dee548f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-7e85-a1fb-ff72812875d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeasesAcquiredInPlaceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-792a-addb-21e70dee548f" xlink:to="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-7e85-a1fb-ff72812875d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceAgreementsMember_019c9bd2-c66d-7b75-8de8-ee3ff232f572" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-792a-addb-21e70dee548f" xlink:to="loc_us-gaap_ServiceAgreementsMember_019c9bd2-c66d-7b75-8de8-ee3ff232f572" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TenantReinsuranceIntangibleMember_019c9bd2-c66d-7a06-89b5-0d3416dce845" xlink:href="nsa-20260331.xsd#nsa_TenantReinsuranceIntangibleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-792a-addb-21e70dee548f" xlink:to="loc_nsa_TenantReinsuranceIntangibleMember_019c9bd2-c66d-7a06-89b5-0d3416dce845" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-78ff-b2e7-1bc35332f88f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-7b10-93bb-88adf4a2216c" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-78ff-b2e7-1bc35332f88f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-78ff-b2e7-1bc35332f88f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-78ff-b2e7-1bc35332f88f" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-78ff-b2e7-1bc35332f88f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7ba6-b563-633628aeccac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-78ff-b2e7-1bc35332f88f" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7ba6-b563-633628aeccac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019c9bd2-c66d-74b8-8c53-b3c34543755a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7ba6-b563-633628aeccac" xlink:to="loc_us-gaap_RelatedPartyMember_019c9bd2-c66d-74b8-8c53-b3c34543755a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7211-bf32-3115dd589e15" xlink:to="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019c9bd2-c66d-72c6-a279-dcbe19e3b9c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019c9bd2-c66d-72c6-a279-dcbe19e3b9c2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019c9bd2-c66d-7696-90be-9a64a8d6fea0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019c9bd2-c66d-7696-90be-9a64a8d6fea0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetAbstract_019c9bd2-c66d-74dd-936b-9d2a77fea5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_AccountsReceivableNetAbstract_019c9bd2-c66d-74dd-936b-9d2a77fea5d7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_019c9bd2-c66d-7518-8868-c0ac93b195e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsReceivableNetAbstract_019c9bd2-c66d-74dd-936b-9d2a77fea5d7" xlink:to="loc_us-gaap_AccountsReceivableNet_019c9bd2-c66d-7518-8868-c0ac93b195e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivables_019c9bd2-c66d-770d-a05f-fe2856534c81" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_OtherReceivables_019c9bd2-c66d-770d-a05f-fe2856534c81" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarnestMoneyDeposits_019c9bd2-c66d-7870-a474-a6c6c19bc12d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarnestMoneyDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_EarnestMoneyDeposits_019c9bd2-c66d-7870-a474-a6c6c19bc12d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019c9bd2-c66d-7c1e-838f-7b2f42fb6e02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_DerivativeAssets_019c9bd2-c66d-7c1e-838f-7b2f42fb6e02" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_019c9bd2-c66d-70e9-89d1-548fcff3a1cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseCurrentAndNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_PrepaidExpenseCurrentAndNoncurrent_019c9bd2-c66d-70e9-89d1-548fcff3a1cd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019c9bd2-c66d-7ac3-ae42-f56d389afac7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019c9bd2-c66d-7ac3-ae42-f56d389afac7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019c9bd2-c66d-77f1-b4cc-391d8444f501" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019c9bd2-c66d-77f1-b4cc-391d8444f501" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019c9bd2-c66d-7a09-bd47-a35a77b7427a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_Goodwill_019c9bd2-c66d-7a09-bd47-a35a77b7427a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssets_019c9bd2-c66d-7766-9281-c6f048250078" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherAssetsAbstract_019c9bd2-c66d-7070-9a13-9cae92629c7d" xlink:to="loc_us-gaap_OtherAssets_019c9bd2-c66d-7766-9281-c6f048250078" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration_019c9bd2-c66d-7c70-908c-15dcff573975" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7211-bf32-3115dd589e15" xlink:to="loc_us-gaap_DerivativeAssetStatementOfFinancialPositionExtensibleEnumeration_019c9bd2-c66d-7c70-908c-15dcff573975" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/OTHERASSETSNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#OTHERASSETSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/OTHERASSETSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7c6c-9122-f48a68b8f172" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-72d7-84fa-1cb05f172ceb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7c6c-9122-f48a68b8f172" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-72d7-84fa-1cb05f172ceb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7436-a609-34810bc7f0c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_019c9bd2-c66d-72d7-84fa-1cb05f172ceb" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7436-a609-34810bc7f0c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7436-a609-34810bc7f0c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7436-a609-34810bc7f0c1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7436-a609-34810bc7f0c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7921-9cc2-af48ab8859ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019c9bd2-c66d-7436-a609-34810bc7f0c1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7921-9cc2-af48ab8859ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-79d3-9905-012fbf2b7a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LeasesAcquiredInPlaceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7921-9cc2-af48ab8859ac" xlink:to="loc_us-gaap_LeasesAcquiredInPlaceMember_019c9bd2-c66d-79d3-9905-012fbf2b7a6b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceAgreementsMember_019c9bd2-c66d-7882-a6ed-105883ae3545" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7921-9cc2-af48ab8859ac" xlink:to="loc_us-gaap_ServiceAgreementsMember_019c9bd2-c66d-7882-a6ed-105883ae3545" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TenantReinsuranceIntangibleMember_019c9bd2-c66d-70bb-9114-39ab030c1b8a" xlink:href="nsa-20260331.xsd#nsa_TenantReinsuranceIntangibleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019c9bd2-c66d-7921-9cc2-af48ab8859ac" xlink:to="loc_nsa_TenantReinsuranceIntangibleMember_019c9bd2-c66d-70bb-9114-39ab030c1b8a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_019c9bd2-c66d-78b3-ba39-23748e4b547b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_019c9bd2-c66d-7c6c-9122-f48a68b8f172" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_019c9bd2-c66d-78b3-ba39-23748e4b547b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/DEBTFINANCINGScheduleofDebtDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#DEBTFINANCINGScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/DEBTFINANCINGScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7276-9400-4edada2fd9c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:to="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7276-9400-4edada2fd9c8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7276-9400-4edada2fd9c8" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-7ed2-8a7a-d106cf9fa38d" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019c9bd2-c66d-70f1-b89c-7147b9732821" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:to="loc_us-gaap_LineOfCreditMember_019c9bd2-c66d-70f1-b89c-7147b9732821" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_019c9bd2-c66d-7c97-9f57-bbd4dd39624c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:to="loc_us-gaap_SecuredDebtMember_019c9bd2-c66d-7c97-9f57-bbd4dd39624c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019c9bd2-c66d-78a9-8234-20f69b4e78ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:to="loc_us-gaap_UnsecuredDebtMember_019c9bd2-c66d-78a9-8234-20f69b4e78ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MortgagesMember_019c9bd2-c66d-7f0e-a5ad-6da54fc107e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7035-8839-63dc87755439" xlink:to="loc_us-gaap_MortgagesMember_019c9bd2-c66d-7f0e-a5ad-6da54fc107e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7001-af93-ec327e8aa810" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7276-9400-4edada2fd9c8" xlink:to="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7001-af93-ec327e8aa810" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7001-af93-ec327e8aa810_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7001-af93-ec327e8aa810" xlink:to="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7001-af93-ec327e8aa810_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-755d-82b2-009b5c010aaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7001-af93-ec327e8aa810" xlink:to="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-755d-82b2-009b5c010aaa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019c9bd2-c66d-7bb2-868e-6c572d84ee3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-755d-82b2-009b5c010aaa" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019c9bd2-c66d-7bb2-868e-6c572d84ee3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TrancheDTermLoanMember_019c9bd2-c66d-7687-a994-82a4da85d518" xlink:href="nsa-20260331.xsd#nsa_TrancheDTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-755d-82b2-009b5c010aaa" xlink:to="loc_nsa_TrancheDTermLoanMember_019c9bd2-c66d-7687-a994-82a4da85d518" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TrancheETermLoanMember_019c9bd2-c66d-7dbe-b1b4-e9dfb722690a" xlink:href="nsa-20260331.xsd#nsa_TrancheETermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-755d-82b2-009b5c010aaa" xlink:to="loc_nsa_TrancheETermLoanMember_019c9bd2-c66d-7dbe-b1b4-e9dfb722690a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-748c-a49b-6c63f95abf2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7276-9400-4edada2fd9c8" xlink:to="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-748c-a49b-6c63f95abf2f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-748c-a49b-6c63f95abf2f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-748c-a49b-6c63f95abf2f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-748c-a49b-6c63f95abf2f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-748c-a49b-6c63f95abf2f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_CreditFacilityMember_019c9bd2-c66d-748b-8f08-a0e38882a024" xlink:href="nsa-20260331.xsd#nsa_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_CreditFacilityMember_019c9bd2-c66d-748b-8f08-a0e38882a024" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2028TermLoanFacilityMember_019c9bd2-c66d-78d2-be05-03ddedc19b79" xlink:href="nsa-20260331.xsd#nsa_A2028TermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_A2028TermLoanFacilityMember_019c9bd2-c66d-78d2-be05-03ddedc19b79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_April2029TermLoanFacilityMember_019c9bd2-c66d-7acb-9b3a-dd4ceec69aa8" xlink:href="nsa-20260331.xsd#nsa_April2029TermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_April2029TermLoanFacilityMember_019c9bd2-c66d-7acb-9b3a-dd4ceec69aa8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_June2029TermLoanFacilityMember_019c9bd2-c66d-70b7-a5c4-49c138335268" xlink:href="nsa-20260331.xsd#nsa_June2029TermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_June2029TermLoanFacilityMember_019c9bd2-c66d-70b7-a5c4-49c138335268" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2026SeniorNotesMember_019c9bd2-c66d-76e0-8c5a-a9335e47f72b" xlink:href="nsa-20260331.xsd#nsa_A2026SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_A2026SeniorNotesMember_019c9bd2-c66d-76e0-8c5a-a9335e47f72b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesOctober2026Member_019c9bd2-c66d-7a92-8dcf-a6dc0d35071d" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesOctober2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesOctober2026Member_019c9bd2-c66d-7a92-8dcf-a6dc0d35071d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesJuly2028Member_019c9bd2-c66d-7b58-b9b1-f14422e339f8" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesJuly2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesJuly2028Member_019c9bd2-c66d-7b58-b9b1-f14422e339f8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesSeptmember2028Member_019c9bd2-c66d-7dda-9680-ec5fbb021d91" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesSeptmember2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesSeptmember2028Member_019c9bd2-c66d-7dda-9680-ec5fbb021d91" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesOctober2028Member_019c9bd2-c66d-7b41-9f27-99e58116aa17" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesOctober2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesOctober2028Member_019c9bd2-c66d-7b41-9f27-99e58116aa17" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2029SeniorNotesMember_019c9bd2-c66d-79d9-ade2-7c692d81171d" xlink:href="nsa-20260331.xsd#nsa_A2029SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_A2029SeniorNotesMember_019c9bd2-c66d-79d9-ade2-7c692d81171d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_August2030SeniorNotesMember_019c9bd2-c66d-7c28-8dd8-92769bc3d6d6" xlink:href="nsa-20260331.xsd#nsa_August2030SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_August2030SeniorNotesMember_019c9bd2-c66d-7c28-8dd8-92769bc3d6d6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_October2030SeniorUnsecuredNotesMember_019c9bd2-c66d-78e3-833b-5f09ba8280e9" xlink:href="nsa-20260331.xsd#nsa_October2030SeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_October2030SeniorUnsecuredNotesMember_019c9bd2-c66d-78e3-833b-5f09ba8280e9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_November2030SeniorNotesMember_019c9bd2-c66d-75ef-92e6-423fd62440d9" xlink:href="nsa-20260331.xsd#nsa_November2030SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_November2030SeniorNotesMember_019c9bd2-c66d-75ef-92e6-423fd62440d9" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_May2031SeniorNotesMember_019c9bd2-c66d-713a-b0ad-459590a3c431" xlink:href="nsa-20260331.xsd#nsa_May2031SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_May2031SeniorNotesMember_019c9bd2-c66d-713a-b0ad-459590a3c431" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_August2031SeniorNotesMember_019c9bd2-c66d-7e45-a2e3-852bd9a8b3a0" xlink:href="nsa-20260331.xsd#nsa_August2031SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_August2031SeniorNotesMember_019c9bd2-c66d-7e45-a2e3-852bd9a8b3a0" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesSeptember2031Member_019c9bd2-c66d-7e98-9d58-d04b12fb5c41" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesSeptember2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesSeptember2031Member_019c9bd2-c66d-7e98-9d58-d04b12fb5c41" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesNovember2031Member_019c9bd2-c66d-7d27-a5f7-4030f42b94a9" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesNovember2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesNovember2031Member_019c9bd2-c66d-7d27-a5f7-4030f42b94a9" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesAugust2032Member_019c9bd2-c66d-7cb9-b746-4712e2ff6919" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesAugust2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesAugust2032Member_019c9bd2-c66d-7cb9-b746-4712e2ff6919" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesNovember2032Member_019c9bd2-c66d-7b54-b1ec-9709b4719e39" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesNovember2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesNovember2032Member_019c9bd2-c66d-7b54-b1ec-9709b4719e39" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesMay2033Member_019c9bd2-c66d-7722-b304-1db0dc9e3d82" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesMay2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesMay2033Member_019c9bd2-c66d-7722-b304-1db0dc9e3d82" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesOctober2033Member_019c9bd2-c66d-761f-876f-0184a9894162" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesOctober2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesOctober2033Member_019c9bd2-c66d-761f-876f-0184a9894162" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_SeniorUnsecuredNotesNovember2033Member_019c9bd2-c66d-7c9b-a7ef-d0f1a11bb961" xlink:href="nsa-20260331.xsd#nsa_SeniorUnsecuredNotesNovember2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_SeniorUnsecuredNotesNovember2033Member_019c9bd2-c66d-7c9b-a7ef-d0f1a11bb961" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2034SeniorUnsecuredNotesMember_019c9bd2-c66d-7a59-bb19-12e8953b3979" xlink:href="nsa-20260331.xsd#nsa_A2034SeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_A2034SeniorUnsecuredNotesMember_019c9bd2-c66d-7a59-bb19-12e8953b3979" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_A2036SeniorUnsecuredNotesMember_019c9bd2-c66d-7717-a555-a63615070d6d" xlink:href="nsa-20260331.xsd#nsa_A2036SeniorUnsecuredNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_A2036SeniorUnsecuredNotesMember_019c9bd2-c66d-7717-a555-a63615070d6d" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FixedRateMortgagesMember_019c9bd2-c66d-74e0-8bdc-b6379a929d5d" xlink:href="nsa-20260331.xsd#nsa_FixedRateMortgagesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7811-9317-e195eff4550f" xlink:to="loc_nsa_FixedRateMortgagesMember_019c9bd2-c66d-74e0-8bdc-b6379a929d5d" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019c9bd2-c66d-742a-8163-4e0d6201b306" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_019c9bd2-c66d-742a-8163-4e0d6201b306" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_DebtLongTermAndShortTermCombinedAmountsGross_019c9bd2-c66d-78ed-895f-83e2b839bd30" xlink:href="nsa-20260331.xsd#nsa_DebtLongTermAndShortTermCombinedAmountsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:to="loc_nsa_DebtLongTermAndShortTermCombinedAmountsGross_019c9bd2-c66d-78ed-895f-83e2b839bd30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019c9bd2-c66d-74a0-8fd6-f64e22243907" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_019c9bd2-c66d-74a0-8fd6-f64e22243907" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_019c9bd2-c66d-7e77-8e6e-32f169aa2a6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-7bca-aa45-d68178d9e1bf" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_019c9bd2-c66d-7e77-8e6e-32f169aa2a6c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/DEBTFINANCINGNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#DEBTFINANCINGNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/DEBTFINANCINGNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7e19-a6c1-075abf01a0aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:to="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7e19-a6c1-075abf01a0aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7ad4-aa03-869f95ce3df5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7e19-a6c1-075abf01a0aa" xlink:to="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7ad4-aa03-869f95ce3df5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7ad4-aa03-869f95ce3df5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7ad4-aa03-869f95ce3df5" xlink:to="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7ad4-aa03-869f95ce3df5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7b60-a297-9afbd16eec6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019c9bd2-c66d-7ad4-aa03-869f95ce3df5" xlink:to="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7b60-a297-9afbd16eec6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019c9bd2-c66d-7bc0-a811-347db47cad76" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7b60-a297-9afbd16eec6a" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019c9bd2-c66d-7bc0-a811-347db47cad76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TrancheDTermLoanMember_019c9bd2-c66d-769c-87c4-c6d33f40b0c9" xlink:href="nsa-20260331.xsd#nsa_TrancheDTermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7b60-a297-9afbd16eec6a" xlink:to="loc_nsa_TrancheDTermLoanMember_019c9bd2-c66d-769c-87c4-c6d33f40b0c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_TrancheETermLoanMember_019c9bd2-c66d-7a15-8ed5-1f7bc186e52f" xlink:href="nsa-20260331.xsd#nsa_TrancheETermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019c9bd2-c66d-7b60-a297-9afbd16eec6a" xlink:to="loc_nsa_TrancheETermLoanMember_019c9bd2-c66d-7a15-8ed5-1f7bc186e52f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-7b93-bd6e-e527c447d136" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7e19-a6c1-075abf01a0aa" xlink:to="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-7b93-bd6e-e527c447d136" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7b93-bd6e-e527c447d136_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-7b93-bd6e-e527c447d136" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-7b93-bd6e-e527c447d136_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-78d9-8961-7ac6d1bad833" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019c9bd2-c66d-7b93-bd6e-e527c447d136" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-78d9-8961-7ac6d1bad833" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_CreditFacilityMember_019c9bd2-c66d-72ec-bc68-e308ffeb40ed" xlink:href="nsa-20260331.xsd#nsa_CreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019c9bd2-c66d-78d9-8961-7ac6d1bad833" xlink:to="loc_nsa_CreditFacilityMember_019c9bd2-c66d-72ec-bc68-e308ffeb40ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-712e-846b-44211c5518db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019c9bd2-c66d-7e19-a6c1-075abf01a0aa" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-712e-846b-44211c5518db" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-712e-846b-44211c5518db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-712e-846b-44211c5518db" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-712e-846b-44211c5518db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7069-b16e-ef3993c501d0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019c9bd2-c66d-712e-846b-44211c5518db" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7069-b16e-ef3993c501d0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019c9bd2-c66d-7276-be76-c5384b1df7ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7069-b16e-ef3993c501d0" xlink:to="loc_us-gaap_LineOfCreditMember_019c9bd2-c66d-7276-be76-c5384b1df7ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_019c9bd2-c66d-74a7-b896-f30685bf4f10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019c9bd2-c66d-7069-b16e-ef3993c501d0" xlink:to="loc_us-gaap_UnsecuredDebtMember_019c9bd2-c66d-74a7-b896-f30685bf4f10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019c9bd2-c66d-74a5-8ca5-199c496bf20c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019c9bd2-c66d-74a5-8ca5-199c496bf20c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LineOfCreditFacilityAccordionFeatureIncreaseLimit_019c9bd2-c66d-7b77-9238-483e94d39aa0" xlink:href="nsa-20260331.xsd#nsa_LineOfCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:to="loc_nsa_LineOfCreditFacilityAccordionFeatureIncreaseLimit_019c9bd2-c66d-7b77-9238-483e94d39aa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_019c9bd2-c66d-7b72-8adf-9e8198003277" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LettersOfCreditOutstandingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_019c9bd2-c66d-7b72-8adf-9e8198003277" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019c9bd2-c66d-710b-a2eb-c7746c910b8b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019c9bd2-c66d-72b1-97d1-c04eeb478b09" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_019c9bd2-c66d-710b-a2eb-c7746c910b8b" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#EARNINGSPERSHARENarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/EARNINGSPERSHARENarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019c9bd2-c66d-7afb-9bf6-8a171ae798f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019c9bd2-c66d-7d34-a1c4-4b06d1835444" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019c9bd2-c66d-7afb-9bf6-8a171ae798f6" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019c9bd2-c66d-7d34-a1c4-4b06d1835444" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019c9bd2-c66d-782a-b555-b33a40ec2899" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019c9bd2-c66d-7d34-a1c4-4b06d1835444" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019c9bd2-c66d-782a-b555-b33a40ec2899" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-782a-b555-b33a40ec2899_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019c9bd2-c66d-782a-b555-b33a40ec2899" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-782a-b555-b33a40ec2899_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-7f44-b794-62656eae3af8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_019c9bd2-c66d-782a-b555-b33a40ec2899" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-7f44-b794-62656eae3af8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LongTermIncentivePlanUnitBasedOnServiceMember_019c9bd2-c66d-7dfd-ac7a-16c1c99b39ab" xlink:href="nsa-20260331.xsd#nsa_LongTermIncentivePlanUnitBasedOnServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-7f44-b794-62656eae3af8" xlink:to="loc_nsa_LongTermIncentivePlanUnitBasedOnServiceMember_019c9bd2-c66d-7dfd-ac7a-16c1c99b39ab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_OPunitsDownREITOPunitsSubordinatedperformanceunitsDownREITsubordinatedperformanceunitsMember_019c9bd2-c66d-7650-8754-db8feac74831" xlink:href="nsa-20260331.xsd#nsa_OPunitsDownREITOPunitsSubordinatedperformanceunitsDownREITsubordinatedperformanceunitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_019c9bd2-c66d-7f44-b794-62656eae3af8" xlink:to="loc_nsa_OPunitsDownREITOPunitsSubordinatedperformanceunitsDownREITsubordinatedperformanceunitsMember_019c9bd2-c66d-7650-8754-db8feac74831" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7090-963e-d5d9180c317f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019c9bd2-c66d-7d34-a1c4-4b06d1835444" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7090-963e-d5d9180c317f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7090-963e-d5d9180c317f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7090-963e-d5d9180c317f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7090-963e-d5d9180c317f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7938-80fb-16ba61ea184e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LimitedPartnersCapitalAccountClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountByClassAxis_019c9bd2-c66d-7090-963e-d5d9180c317f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7938-80fb-16ba61ea184e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7393-ac3d-d9a22e3110e1" xlink:href="nsa-20260331.xsd#nsa_ClassAUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7938-80fb-16ba61ea184e" xlink:to="loc_nsa_ClassAUnitsMember_019c9bd2-c66d-7393-ac3d-d9a22e3110e1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7c20-98c6-443c51bb1b2a" xlink:href="nsa-20260331.xsd#nsa_LongTermIncentivePlanUnitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LimitedPartnersCapitalAccountClassDomain_019c9bd2-c66d-7938-80fb-16ba61ea184e" xlink:to="loc_nsa_LongTermIncentivePlanUnitMember_019c9bd2-c66d-7c20-98c6-443c51bb1b2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_019c9bd2-c66d-7d34-a1c4-4b06d1835444" xlink:to="loc_dei_LegalEntityAxis_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019c9bd2-c66d-74a9-b4f2-cdd07a45beae" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019c9bd2-c66d-79b2-b18f-1fb06b3c29e9" xlink:to="loc_dei_EntityDomain_019c9bd2-c66d-74a9-b4f2-cdd07a45beae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NSAOPLPMember_019c9bd2-c66d-70b9-857c-cddfe2905eb3" xlink:href="nsa-20260331.xsd#nsa_NSAOPLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c9bd2-c66d-74a9-b4f2-cdd07a45beae" xlink:to="loc_nsa_NSAOPLPMember_019c9bd2-c66d-70b9-857c-cddfe2905eb3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-7af8-bb90-e109516bd339" xlink:href="nsa-20260331.xsd#nsa_DownREITPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019c9bd2-c66d-74a9-b4f2-cdd07a45beae" xlink:to="loc_nsa_DownREITPartnershipMember_019c9bd2-c66d-7af8-bb90-e109516bd339" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_EquityInstrumentConvertibleConversionRatio_019c9bd2-c66d-79ff-9877-2f15262659c0" xlink:href="nsa-20260331.xsd#nsa_EquityInstrumentConvertibleConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019c9bd2-c66d-7afb-9bf6-8a171ae798f6" xlink:to="loc_nsa_EquityInstrumentConvertibleConversionRatio_019c9bd2-c66d-79ff-9877-2f15262659c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019c9bd2-c66d-7fe8-9286-db3349a463da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_019c9bd2-c66d-7afb-9bf6-8a171ae798f6" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_019c9bd2-c66d-7fe8-9286-db3349a463da" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSScheduleofInterestRateSwapDerivativesMeasuredatFairValueDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#FAIRVALUEMEASUREMENTSScheduleofInterestRateSwapDerivativesMeasuredatFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSScheduleofInterestRateSwapDerivativesMeasuredatFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d75-a141-30dac516319e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d75-a141-30dac516319e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-72a3-8964-4d5d336b0c51" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d75-a141-30dac516319e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-72a3-8964-4d5d336b0c51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-72a3-8964-4d5d336b0c51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-72a3-8964-4d5d336b0c51" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-72a3-8964-4d5d336b0c51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-77e4-b4f5-913acb2b2253" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-72a3-8964-4d5d336b0c51" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-77e4-b4f5-913acb2b2253" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c9bd2-c66d-79d1-acf0-eb627a6b1782" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-77e4-b4f5-913acb2b2253" xlink:to="loc_us-gaap_InterestRateSwapMember_019c9bd2-c66d-79d1-acf0-eb627a6b1782" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d75-a141-30dac516319e" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9bd2-c66d-7a9c-b3a7-463960877322" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019c9bd2-c66d-79db-b3d1-a5dc2a685ab8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9bd2-c66d-7a9c-b3a7-463960877322" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019c9bd2-c66d-7e64-bf40-c32e5c383897" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019c9bd2-c66d-7a9c-b3a7-463960877322" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019c9bd2-c66d-7e64-bf40-c32e5c383897" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-7c7a-90ce-f6125a2506d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d75-a141-30dac516319e" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-7c7a-90ce-f6125a2506d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-7c7a-90ce-f6125a2506d1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-7c7a-90ce-f6125a2506d1" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-7c7a-90ce-f6125a2506d1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-75ba-a944-9e55e90180cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-7c7a-90ce-f6125a2506d1" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-75ba-a944-9e55e90180cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c9bd2-c66d-7d44-b684-091d99039331" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-75ba-a944-9e55e90180cf" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c9bd2-c66d-7d44-b684-091d99039331" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfInterestRateDerivativesHeld_019c9bd2-c66d-7727-98a6-15d863fabb8d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfInterestRateDerivativesHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_us-gaap_NumberOfInterestRateDerivativesHeld_019c9bd2-c66d-7727-98a6-15d863fabb8d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c9bd2-c66d-7167-adef-839c83ef9b52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c9bd2-c66d-7167-adef-839c83ef9b52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c9bd2-c66d-764d-a4b2-f2d729c3fe01" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeAsset_019c9bd2-c66d-764d-a4b2-f2d729c3fe01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c9bd2-c66d-7426-a1c0-9da7a6433786" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeFairValueOfDerivativeLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_us-gaap_DerivativeFairValueOfDerivativeLiability_019c9bd2-c66d-7426-a1c0-9da7a6433786" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward_019c9bd2-c66d-70c9-ac78-caf38c87e413" xlink:href="nsa-20260331.xsd#nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7d9f-8926-1da1e60043bc" xlink:to="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward_019c9bd2-c66d-70c9-ac78-caf38c87e413" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasis_019c9bd2-c66d-7748-8f0f-e41c622816ce" xlink:href="nsa-20260331.xsd#nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward_019c9bd2-c66d-70c9-ac78-caf38c87e413" xlink:to="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasis_019c9bd2-c66d-7748-8f0f-e41c622816ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInEarningsReclassificationFromAOCICurrentPeriod_019c9bd2-c66d-70ee-b15f-6fe5126bfbaa" xlink:href="nsa-20260331.xsd#nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInEarningsReclassificationFromAOCICurrentPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward_019c9bd2-c66d-70c9-ac78-caf38c87e413" xlink:to="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInEarningsReclassificationFromAOCICurrentPeriod_019c9bd2-c66d-70ee-b15f-6fe5126bfbaa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInOtherComprehensiveIncomeLoss_019c9bd2-c66d-7fc2-b8ff-c3f3a1272607" xlink:href="nsa-20260331.xsd#nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInOtherComprehensiveIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisRollForward_019c9bd2-c66d-70c9-ac78-caf38c87e413" xlink:to="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisGainLossIncludedInOtherComprehensiveIncomeLoss_019c9bd2-c66d-7fc2-b8ff-c3f3a1272607" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasis_019c9bd2-c66d-7bdb-a055-4e0b0d236abf" xlink:href="nsa-20260331.xsd#nsa_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasis"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#FAIRVALUEMEASUREMENTSNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d36-97f6-c5a0ed034fba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d36-97f6-c5a0ed034fba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-77f3-99bc-a410c4e31f2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d36-97f6-c5a0ed034fba" xlink:to="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-77f3-99bc-a410c4e31f2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-77f3-99bc-a410c4e31f2c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-77f3-99bc-a410c4e31f2c" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-77f3-99bc-a410c4e31f2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-72ee-9e73-8c90e02e6270" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019c9bd2-c66d-77f3-99bc-a410c4e31f2c" xlink:to="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-72ee-9e73-8c90e02e6270" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c9bd2-c66d-7b77-a8a7-d9b9732e6e7b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019c9bd2-c66d-72ee-9e73-8c90e02e6270" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_019c9bd2-c66d-7b77-a8a7-d9b9732e6e7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-7a2d-a28d-f46f78961e4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d36-97f6-c5a0ed034fba" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-7a2d-a28d-f46f78961e4b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7a2d-a28d-f46f78961e4b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-7a2d-a28d-f46f78961e4b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7a2d-a28d-f46f78961e4b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7724-9d60-debe96df1b10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019c9bd2-c66d-7a2d-a28d-f46f78961e4b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7724-9d60-debe96df1b10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_019c9bd2-c66d-73e8-bc32-fcdeeaf2272b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7724-9d60-debe96df1b10" xlink:to="loc_us-gaap_InterestRateSwapMember_019c9bd2-c66d-73e8-bc32-fcdeeaf2272b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ForwardStartingSwapsMember_019c9bd2-c66d-726b-bb08-1188a6b88168" xlink:href="nsa-20260331.xsd#nsa_ForwardStartingSwapsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019c9bd2-c66d-7724-9d60-debe96df1b10" xlink:to="loc_nsa_ForwardStartingSwapsMember_019c9bd2-c66d-726b-bb08-1188a6b88168" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c9bd2-c66d-7733-a211-9818ff99035c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-7d36-97f6-c5a0ed034fba" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c9bd2-c66d-7733-a211-9818ff99035c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c9bd2-c66d-7733-a211-9818ff99035c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c9bd2-c66d-7733-a211-9818ff99035c" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c9bd2-c66d-7733-a211-9818ff99035c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_019c9bd2-c66d-7202-90aa-619de9522854" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_019c9bd2-c66d-7733-a211-9818ff99035c" xlink:to="loc_us-gaap_HedgingRelationshipDomain_019c9bd2-c66d-7202-90aa-619de9522854" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_019c9bd2-c66d-700f-b71d-a0dfe5390cb1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_019c9bd2-c66d-7202-90aa-619de9522854" xlink:to="loc_us-gaap_CashFlowHedgingMember_019c9bd2-c66d-700f-b71d-a0dfe5390cb1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019c9bd2-c66d-782d-b11a-428e16506db0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019c9bd2-c66d-782d-b11a-428e16506db0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageRemainingMaturity1_019c9bd2-c66d-7196-8f6c-a9497e5c5f70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAverageRemainingMaturity1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_DerivativeAverageRemainingMaturity1_019c9bd2-c66d-7196-8f6c-a9497e5c5f70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeForwardInterestRate_019c9bd2-c66d-7aa1-ad3c-f05ee96f2477" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeForwardInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_DerivativeForwardInterestRate_019c9bd2-c66d-7aa1-ad3c-f05ee96f2477" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_RealizedGainLossCashFlowHedge_019c9bd2-c66d-7898-88fb-14f779e11283" xlink:href="nsa-20260331.xsd#nsa_RealizedGainLossCashFlowHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_nsa_RealizedGainLossCashFlowHedge_019c9bd2-c66d-7898-88fb-14f779e11283" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTermOfContract_019c9bd2-c66d-70d7-a2a9-61f935d2f9f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_DerivativeTermOfContract_019c9bd2-c66d-70d7-a2a9-61f935d2f9f9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_019c9bd2-c66d-7c6c-93ca-ccad166bb7eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_019c9bd2-c66d-7c6c-93ca-ccad166bb7eb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAverageFixedInterestRate_019c9bd2-c66d-7bdc-9ab3-3f51c5a51fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAverageFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7aa7-a421-980a79538ada" xlink:to="loc_us-gaap_DerivativeAverageFixedInterestRate_019c9bd2-c66d-7bdc-9ab3-3f51c5a51fe9" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSScheduleofCarryingValuesandEstimatedFairValuesofDebtInstrumentsDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#FAIRVALUEMEASUREMENTSScheduleofCarryingValuesandEstimatedFairValuesofDebtInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/FAIRVALUEMEASUREMENTSScheduleofCarryingValuesandEstimatedFairValuesofDebtInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7ae2-ab28-8aed644dc4c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-71a7-881f-410c0394df21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7ae2-ab28-8aed644dc4c3" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-71a7-881f-410c0394df21" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019c9bd2-c66d-71a7-881f-410c0394df21" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c9bd2-c66d-73e5-be5a-9c36a23c34c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019c9bd2-c66d-7c9e-a3b0-ac51c2e0f225" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c9bd2-c66d-73e5-be5a-9c36a23c34c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7231-8ad5-75947af29e1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019c9bd2-c66d-73e5-be5a-9c36a23c34c3" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7231-8ad5-75947af29e1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c9bd2-c66d-7bc3-a740-3f8bd657ff15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7231-8ad5-75947af29e1e" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019c9bd2-c66d-7bc3-a740-3f8bd657ff15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c9bd2-c66d-7ff1-bd65-5f3a100fb764" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019c9bd2-c66d-7231-8ad5-75947af29e1e" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019c9bd2-c66d-7ff1-bd65-5f3a100fb764" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NotesPayableFairValueDisclosure_019c9bd2-c66d-74f2-9d7e-658697f16a65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NotesPayableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7ae2-ab28-8aed644dc4c3" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_019c9bd2-c66d-74f2-9d7e-658697f16a65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableFairValueDisclosure_019c9bd2-c66d-7a92-9caf-29da07698f60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LoansPayableFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019c9bd2-c66d-7ae2-ab28-8aed644dc4c3" xlink:to="loc_us-gaap_LoansPayableFairValueDisclosure_019c9bd2-c66d-7a92-9caf-29da07698f60" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleofReportingSegmentNOIDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SegmentsScheduleofReportingSegmentNOIDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleofReportingSegmentNOIDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingAssetReconcilingItemLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-74d8-8ece-f9b6d464c9e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-74d8-8ece-f9b6d464c9e1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-74b7-b705-0698d60e6076" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-74d8-8ece-f9b6d464c9e1" xlink:to="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-74b7-b705-0698d60e6076" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-74b7-b705-0698d60e6076_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-74b7-b705-0698d60e6076" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-74b7-b705-0698d60e6076_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-77db-b740-979f6613bec7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-74b7-b705-0698d60e6076" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-77db-b740-979f6613bec7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c66d-73be-bed9-f0c1bcfad975" xlink:href="nsa-20260331.xsd#nsa_PropertyRelatedOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-77db-b740-979f6613bec7" xlink:to="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c66d-73be-bed9-f0c1bcfad975" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-72e6-8449-873e6f895616" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-74d8-8ece-f9b6d464c9e1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-72e6-8449-873e6f895616" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-72e6-8449-873e6f895616_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-72e6-8449-873e6f895616" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-72e6-8449-873e6f895616_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-759a-87cc-f472c52f2c04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-72e6-8449-873e6f895616" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-759a-87cc-f472c52f2c04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7071-953c-7b4a28485e7a" xlink:href="nsa-20260331.xsd#nsa_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c9bd2-c66d-759a-87cc-f472c52f2c04" xlink:to="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7071-953c-7b4a28485e7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c66d-77b2-a70b-55743247feea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c66d-77b2-a70b-55743247feea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-74ec-b7bf-d54458fc8506" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-74ec-b7bf-d54458fc8506" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_RevenueAdjusted_019c9bd2-c66d-7228-a3a8-49ba905b2164" xlink:href="nsa-20260331.xsd#nsa_RevenueAdjusted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_nsa_RevenueAdjusted_019c9bd2-c66d-7228-a3a8-49ba905b2164" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_StorePayrollAndRelatedCosts_019c9bd2-c66d-7d01-bd1b-e78a51912119" xlink:href="nsa-20260331.xsd#nsa_StorePayrollAndRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_nsa_StorePayrollAndRelatedCosts_019c9bd2-c66d-7d01-bd1b-e78a51912119" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RealEstateTaxExpense_019c9bd2-c66d-7481-9877-1bb980b632ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RealEstateTaxExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_RealEstateTaxExpense_019c9bd2-c66d-7481-9877-1bb980b632ee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UtilitiesOperatingExpense_019c9bd2-c66d-7abf-8db0-c4a9c41e3e7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UtilitiesOperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_UtilitiesOperatingExpense_019c9bd2-c66d-7abf-8db0-c4a9c41e3e7d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseMaintenance_019c9bd2-c66d-74db-8022-9f9b64b6d37b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UtilitiesOperatingExpenseMaintenance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseMaintenance_019c9bd2-c66d-74db-8022-9f9b64b6d37b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MarketingExpense_019c9bd2-c66d-7bdf-bd51-bef7136db710" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_MarketingExpense_019c9bd2-c66d-7bdf-bd51-bef7136db710" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralInsuranceExpense_019c9bd2-c66d-7ce8-afbb-0ce78e1550af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralInsuranceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_GeneralInsuranceExpense_019c9bd2-c66d-7ce8-afbb-0ce78e1550af" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfOtherPropertyOperatingExpense_019c9bd2-c66d-723c-864d-f1696a557255" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfOtherPropertyOperatingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_CostOfOtherPropertyOperatingExpense_019c9bd2-c66d-723c-864d-f1696a557255" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingCostsAndExpenses_019c9bd2-c66d-7e06-b8b4-73974a329c8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingCostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_OperatingCostsAndExpenses_019c9bd2-c66d-7e06-b8b4-73974a329c8e" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019c9bd2-c66d-73b8-b77e-c3c42a4894b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-76db-9c21-cfad8c28a3b9" xlink:to="loc_us-gaap_OperatingIncomeLoss_019c9bd2-c66d-73b8-b77e-c3c42a4894b5" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleOfReconciliationOfOurReportableSegmentRevenueToTotalRevenueDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SegmentsScheduleOfReconciliationOfOurReportableSegmentRevenueToTotalRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleOfReconciliationOfOurReportableSegmentRevenueToTotalRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingAssetReconcilingItemLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-7570-aa80-1a17afc35562" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:to="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-7570-aa80-1a17afc35562" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-722c-8a86-b3f8a9e3e456" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-7570-aa80-1a17afc35562" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-722c-8a86-b3f8a9e3e456" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-722c-8a86-b3f8a9e3e456_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-722c-8a86-b3f8a9e3e456" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-722c-8a86-b3f8a9e3e456_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7458-ab9a-0dc15e9282d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-722c-8a86-b3f8a9e3e456" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7458-ab9a-0dc15e9282d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7556-9dc3-cb18da6eb221" xlink:href="nsa-20260331.xsd#nsa_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7458-ab9a-0dc15e9282d1" xlink:to="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7556-9dc3-cb18da6eb221" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7330-8b59-237413f9f7ee" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfAssetsFromSegmentToConsolidatedTable_019c9bd2-c66d-7570-aa80-1a17afc35562" xlink:to="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7330-8b59-237413f9f7ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-7330-8b59-237413f9f7ee_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7330-8b59-237413f9f7ee" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-7330-8b59-237413f9f7ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-79dd-aaac-5ecb474d8a1c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7330-8b59-237413f9f7ee" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-79dd-aaac-5ecb474d8a1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c66d-79b9-afcc-ebe113af1c79" xlink:href="nsa-20260331.xsd#nsa_PropertyRelatedOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-79dd-aaac-5ecb474d8a1c" xlink:to="loc_nsa_PropertyRelatedOtherMember_019c9bd2-c66d-79b9-afcc-ebe113af1c79" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c66d-7c03-be1a-d9ea9d23b943" xlink:href="nsa-20260331.xsd#nsa_ManagementFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-79dd-aaac-5ecb474d8a1c" xlink:to="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c66d-7c03-be1a-d9ea9d23b943" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c66d-7bd6-b35f-ecf8553fe74f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_019c9bd2-c66d-7bd6-b35f-ecf8553fe74f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-706a-a620-27fd8c786c7d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-706a-a620-27fd8c786c7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_RevenueAdjusted_019c9bd2-c66d-7535-a410-134ab0c5576c" xlink:href="nsa-20260331.xsd#nsa_RevenueAdjusted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:to="loc_nsa_RevenueAdjusted_019c9bd2-c66d-7535-a410-134ab0c5576c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019c9bd2-c66d-70df-93fa-793227aefd13" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingAssetReconcilingItemLineItems_019c9bd2-c66d-7a06-b2df-21cce5136a52" xlink:to="loc_us-gaap_Revenues_019c9bd2-c66d-70df-93fa-793227aefd13" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleOfReconciliationOfOurReportedIncomeBeforeIncomeTaxesToOurNetOperatingIncomeDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SegmentsScheduleOfReconciliationOfOurReportedIncomeBeforeIncomeTaxesToOurNetOperatingIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SegmentsScheduleOfReconciliationOfOurReportedIncomeBeforeIncomeTaxesToOurNetOperatingIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_019c9bd2-c66d-7e73-808b-d0d5c5380216" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_019c9bd2-c66d-7e73-808b-d0d5c5380216" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-731c-8e2a-c7129aabce5c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_019c9bd2-c66d-7e73-808b-d0d5c5380216" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-731c-8e2a-c7129aabce5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-731c-8e2a-c7129aabce5c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-731c-8e2a-c7129aabce5c" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-731c-8e2a-c7129aabce5c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7294-93a5-12ce19ab3f72" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019c9bd2-c66d-731c-8e2a-c7129aabce5c" xlink:to="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7294-93a5-12ce19ab3f72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7181-9a5f-4b416d58a963" xlink:href="nsa-20260331.xsd#nsa_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019c9bd2-c66d-7294-93a5-12ce19ab3f72" xlink:to="loc_nsa_ReportableSegmentMember_019c9bd2-c66d-7181-9a5f-4b416d58a963" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_019c9bd2-c66d-7e73-808b-d0d5c5380216" xlink:to="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-76f5-b6a6-724004998bfb" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019c9bd2-c66d-7271-ab6c-5ca9b5a4ad69" xlink:to="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-76f5-b6a6-724004998bfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c66d-7c5c-be12-d907a06fac2a" xlink:href="nsa-20260331.xsd#nsa_ManagementFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019c9bd2-c66d-76f5-b6a6-724004998bfb" xlink:to="loc_nsa_ManagementFeesAndOtherMember_019c9bd2-c66d-7c5c-be12-d907a06fac2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9bd2-c66d-71eb-876d-2b5ee8779def" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019c9bd2-c66d-71eb-876d-2b5ee8779def" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-7b20-b9fc-b843c281d6b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019c9bd2-c66d-7b20-b9fc-b843c281d6b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019c9bd2-c66d-79e3-8afd-a7749f364cfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019c9bd2-c66d-79e3-8afd-a7749f364cfe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c66d-7c3b-b909-e8419e4b79ae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_DepreciationAndAmortization_019c9bd2-c66d-7c3b-b909-e8419e4b79ae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherGeneralExpense_019c9bd2-c66d-79dd-99d6-d715f34b64e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherGeneralExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_OtherGeneralExpense_019c9bd2-c66d-79dd-99d6-d715f34b64e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c66d-7f17-960d-7361aa4cf460" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_InterestExpenseNonoperating_019c9bd2-c66d-7f17-960d-7361aa4cf460" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c9bd2-c66d-710d-840b-bd470c52795c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_019c9bd2-c66d-710d-840b-bd470c52795c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019d961c-f107-7cb6-b785-963b240ec89e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_019d961c-f107-7cb6-b785-963b240ec89e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_019da02a-c89a-767e-a8c0-96de6261ca6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationIntegrationRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_BusinessCombinationIntegrationRelatedCosts_019da02a-c89a-767e-a8c0-96de6261ca6b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c66d-70b8-98e1-84221f7e012b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019c9bd2-c66d-70b8-98e1-84221f7e012b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_019c9bd2-c66d-7ad1-8b09-9a21a0e588b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_019c9bd2-c66d-7ad1-8b09-9a21a0e588b0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019c9bd2-c66d-7e2a-a31a-8bee9e8df7a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_019c9bd2-c66d-74f6-962a-40f620f9b218" xlink:to="loc_us-gaap_OperatingIncomeLoss_019c9bd2-c66d-7e2a-a31a-8bee9e8df7a2" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nationalstorageaffiliates.com/role/SUBSEQUENTEVENTSDetails" xlink:type="simple" xlink:href="nsa-20260331.xsd#SUBSEQUENTEVENTSDetails"/>
  <link:definitionLink xlink:role="http://www.nationalstorageaffiliates.com/role/SUBSEQUENTEVENTSDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019c9bd2-c66d-7661-a291-1b48d2c36dd1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019c9bd2-c66d-7454-9886-dc26f4f9d95e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019c9bd2-c66d-7661-a291-1b48d2c36dd1" xlink:to="loc_us-gaap_SubsequentEventTable_019c9bd2-c66d-7454-9886-dc26f4f9d95e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-756b-a53d-18cdcbdd7371" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019c9bd2-c66d-7454-9886-dc26f4f9d95e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-756b-a53d-18cdcbdd7371" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-756b-a53d-18cdcbdd7371_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-756b-a53d-18cdcbdd7371" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-756b-a53d-18cdcbdd7371_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7e80-8040-9be1b54c6500" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019c9bd2-c66d-756b-a53d-18cdcbdd7371" xlink:to="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7e80-8040-9be1b54c6500" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_ThirdPartyMember_019c9bd2-c66d-737a-a0bc-4506e6fa83f2" xlink:href="nsa-20260331.xsd#nsa_ThirdPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019c9bd2-c66d-7e80-8040-9be1b54c6500" xlink:to="loc_nsa_ThirdPartyMember_019c9bd2-c66d-737a-a0bc-4506e6fa83f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_019c9bd2-c66d-77bf-8987-7302df2368b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019c9bd2-c66d-7454-9886-dc26f4f9d95e" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_019c9bd2-c66d-77bf-8987-7302df2368b5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019c9bd2-c66d-77bf-8987-7302df2368b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019c9bd2-c66d-77bf-8987-7302df2368b5" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019c9bd2-c66d-77bf-8987-7302df2368b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_019c9bd2-c66d-7bde-b1e0-5d0d900659a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_019c9bd2-c66d-77bf-8987-7302df2368b5" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_019c9bd2-c66d-7bde-b1e0-5d0d900659a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019c9bd2-c66d-7fc7-9b44-069bbd44052c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DiscontinuedOperationsHeldforsaleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_019c9bd2-c66d-7bde-b1e0-5d0d900659a4" xlink:to="loc_us-gaap_DiscontinuedOperationsHeldforsaleMember_019c9bd2-c66d-7fc7-9b44-069bbd44052c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019d95fe-b373-79ba-8f6b-8acb48d53af5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019c9bd2-c66d-7454-9886-dc26f4f9d95e" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019d95fe-b373-79ba-8f6b-8acb48d53af5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d95fe-b373-79ba-8f6b-8acb48d53af5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d95fe-b373-79ba-8f6b-8acb48d53af5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d95fe-b373-79ba-8f6b-8acb48d53af5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019d95fe-b373-78d8-a486-ebc6a2a878ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019d95fe-b373-79ba-8f6b-8acb48d53af5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019d95fe-b373-78d8-a486-ebc6a2a878ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019d95fe-de41-7849-b762-353204be7e35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019d95fe-b373-78d8-a486-ebc6a2a878ec" xlink:to="loc_us-gaap_SubsequentEventMember_019d95fe-de41-7849-b762-353204be7e35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019c9bd2-c66d-7373-be27-8601a0dfa54c" xlink:href="nsa-20260331.xsd#nsa_NumberOfRealEstatePropertiesToBeDisposedOf"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019c9bd2-c66d-7661-a291-1b48d2c36dd1" xlink:to="loc_nsa_NumberOfRealEstatePropertiesToBeDisposedOf_019c9bd2-c66d-7373-be27-8601a0dfa54c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019c9bd2-c66d-722b-88e1-8272ad755188" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019c9bd2-c66d-7661-a291-1b48d2c36dd1" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_019c9bd2-c66d-722b-88e1-8272ad755188" xlink:type="arc" order="1"/>
  </link:definitionLink>
</link:linkbase>
