<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0609</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-08-17</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001456772</issuerCik>
        <issuerName>OFFICE PROPERTIES INCOME TRUST</issuerName>
        <issuerTradingSymbol>OPI</issuerTradingSymbol>
        <issuerForeignTradingSymbol></issuerForeignTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001316622</rptOwnerCik>
            <rptOwnerName>REDWOOD CAPITAL MANAGEMENT, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>250 WEST 55TH ST.</rptOwnerStreet1>
            <rptOwnerStreet2>26TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001737513</rptOwnerCik>
            <rptOwnerName>Redwood Capital Management Holdings, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>250 WEST 55TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2>26TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002142105</rptOwnerCik>
            <rptOwnerName>Double Twins K, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>250 W 55TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001930856</rptOwnerCik>
            <rptOwnerName>KLIKSBERG RUBEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerNonUSAddressFlag>false</rptOwnerNonUSAddressFlag>
            <rptOwnerStreet1>C/O REDWOOD CAPITAL MANAGEMENT, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>250 WEST 55TH STREET, 26TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares of Beneficial Interest</value>
            </securityTitle>
            <transactionDate>
                <value>2026-08-17</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20686</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.0260</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4137726</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares of Beneficial Interest</value>
            </securityTitle>
            <transactionDate>
                <value>2026-08-18</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>175734</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.0324</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>3961992</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.00 - $19.20. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission (the &quot;SEC&quot;), upon request, full information regarding the number of shares bought at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
        <footnote id="F2">This Form 4 is being filed jointly by Redwood Capital Management, LLC, a Delaware limited liability company (&quot;Redwood Capital Management&quot;), Redwood Capital Management Holdings, LP, a Delaware limited partnership (&quot;Redwood Capital Management Holdings&quot;), Double Twins K, LLC, a Delaware limited liability company (&quot;Double Twins K&quot;), and Ruben Kliksberg, a citizen of the United States of America (collectively, the &quot;Reporting Persons&quot;), each of whom may be deemed to have a pecuniary interest in securities reported on this Form 4 (the &quot;Subject Securities&quot;). The business address of each Reporting Person is 250 West 55th St., 26th Floor, New York, NY 10019.</footnote>
        <footnote id="F3">The Subject Securities are directly held by certain funds (the &quot;Redwood Funds&quot;) for which Redwood Capital Management serves as the investment manager. Each of (a) Redwood Capital Management, as the investment manager to the Redwood Funds with respect to the Subject Securities directly held by the Redwood Funds, (b) Redwood Capital Management Holdings, as the sole member of Redwood Capital Management, (c) Double Twins K, as the general partner of Redwood Capital Management Holdings, and (d) Mr. Kliksberg, as the managing member of Double Twins K, may be deemed to be the beneficial owner of the Subject Securities for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended. Each Reporting Person disclaims any beneficial ownership of the Subject Securities, except to the extent of any pecuniary interest therein.</footnote>
        <footnote id="F4">The price reported is a weighted average price. These shares were sold in multiple transactions at prices ranging from $19.00 - $19.30. The reporting persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission the SEC, upon request, full information regarding the number of shares bought at each separate price within the ranges set forth in this footnote to this Form 4.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Redwood Capital Management, LLC, By: /s/ Redwood Capital Management Holdings, LP, its sole member, By: Double Twins K, LLC, its general partner, By: /s/ Ruben Kliksberg, its Managing Member</signatureName>
        <signatureDate>2026-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Redwood Capital Management Holdings, LP, By: Double Twins K, LLC, its general partner, By: /s/ Ruben Kliksberg, its Managing Member</signatureName>
        <signatureDate>2026-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>Double Twins K, LLC, By: /s/ Ruben Kliksberg, its Managing Member</signatureName>
        <signatureDate>2026-08-19</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ruben Kliksberg</signatureName>
        <signatureDate>2026-08-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
