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

    <schemaVersion>X0708</schemaVersion>

    <submissionType>D/A</submissionType>

    <testOrLive>LIVE</testOrLive>

    <primaryIssuer>
        <cik>0002064933</cik>
        <entityName>Keystone Long Only Fund</entityName>
        <issuerAddress>
            <street1>C/O WALKERS CORPORATE LIMITED</street1>
            <street2>190 ELGIN AVENUE</street2>
            <city>GEORGE TOWN, GRAND CAYMAN</city>
            <stateOrCountry>E9</stateOrCountry>
            <stateOrCountryDescription>CAYMAN ISLANDS</stateOrCountryDescription>
            <zipCode>KY1-9008</zipCode>
        </issuerAddress>
        <issuerPhoneNumber>65 60371200</issuerPhoneNumber>
        <jurisdictionOfInc>CAYMAN ISLANDS</jurisdictionOfInc>
        <issuerPreviousNameList>
            <value>None</value>
        </issuerPreviousNameList>
        <edgarPreviousNameList>
            <value>None</value>
        </edgarPreviousNameList>
        <entityType>Other</entityType>
        <entityTypeOtherDesc>Cayman Islands Exempted Company</entityTypeOtherDesc>
        <yearOfInc>
            <withinFiveYears>true</withinFiveYears>
            <value>2025</value>
        </yearOfInc>
    </primaryIssuer>

    <relatedPersonsList>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>SIMON</firstName>
                <lastName>COX</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>C/O WALKERS CORPORATE LIMITED</street1>
                <street2>190 ELGIN STREET</street2>
                <city>GEORGE TOWN GRAND CAYMAN</city>
                <stateOrCountry>E9</stateOrCountry>
                <stateOrCountryDescription>CAYMAN ISLANDS</stateOrCountryDescription>
                <zipCode>KY1-9008</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>JOSEPHINE</firstName>
                <lastName>ORGILL</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>C/O WALKERS CORPORATE LIMITED</street1>
                <street2>190 ELGIN STREET</street2>
                <city>GEORGE TOWN GRAND CAYMAN</city>
                <stateOrCountry>E9</stateOrCountry>
                <stateOrCountryDescription>CAYMAN ISLANDS</stateOrCountryDescription>
                <zipCode>KY1-9008</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
        <relatedPersonInfo>
            <relatedPersonName>
                <firstName>XUAN</firstName>
                <lastName>LIU</lastName>
            </relatedPersonName>
            <relatedPersonAddress>
                <street1>C/O WALKERS CORPORATE LIMITED</street1>
                <street2>190 ELGIN STREET</street2>
                <city>GEORGE TOWN GRAND CAYMAN</city>
                <stateOrCountry>E9</stateOrCountry>
                <stateOrCountryDescription>CAYMAN ISLANDS</stateOrCountryDescription>
                <zipCode>KY1-9008</zipCode>
            </relatedPersonAddress>
            <relatedPersonRelationshipList>
                <relationship>Director</relationship>
            </relatedPersonRelationshipList>
            <relationshipClarification></relationshipClarification>
        </relatedPersonInfo>
    </relatedPersonsList>

    <offeringData>
        <industryGroup>
            <industryGroupType>Pooled Investment Fund</industryGroupType>
            <investmentFundInfo>
                <investmentFundType>Hedge Fund</investmentFundType>
                <is40Act>false</is40Act>
            </investmentFundInfo>
        </industryGroup>
        <issuerSize>
            <aggregateNetAssetValueRange>Decline to Disclose</aggregateNetAssetValueRange>
        </issuerSize>
        <federalExemptionsExclusions>
            <item>06b</item>
            <item>3C</item>
            <item>3C.7</item>
        </federalExemptionsExclusions>
        <typeOfFiling>
            <newOrAmendment>
                <isAmendment>true</isAmendment>
                <previousAccessionNumber>0002024908-26-000006</previousAccessionNumber>
            </newOrAmendment>
            <dateOfFirstSale>
                <value>2026-05-01</value>
            </dateOfFirstSale>
        </typeOfFiling>
        <durationOfOffering>
            <moreThanOneYear>true</moreThanOneYear>
        </durationOfOffering>
        <typesOfSecuritiesOffered>
            <isPooledInvestmentFundType>true</isPooledInvestmentFundType>
        </typesOfSecuritiesOffered>
        <businessCombinationTransaction>
            <isBusinessCombinationTransaction>false</isBusinessCombinationTransaction>
            <clarificationOfResponse></clarificationOfResponse>
        </businessCombinationTransaction>
        <minimumInvestmentAccepted>1000000</minimumInvestmentAccepted>
        <salesCompensationList></salesCompensationList>
        <offeringSalesAmounts>
            <totalOfferingAmount>Indefinite</totalOfferingAmount>
            <totalAmountSold>16800000</totalAmountSold>
            <totalRemaining>Indefinite</totalRemaining>
            <clarificationOfResponse></clarificationOfResponse>
        </offeringSalesAmounts>
        <investors>
            <hasNonAccreditedInvestors>false</hasNonAccreditedInvestors>
            <totalNumberAlreadyInvested>7</totalNumberAlreadyInvested>
        </investors>
        <salesCommissionsFindersFees>
            <salesCommissions>
                <dollarAmount>0</dollarAmount>
            </salesCommissions>
            <findersFees>
                <dollarAmount>0</dollarAmount>
            </findersFees>
            <clarificationOfResponse></clarificationOfResponse>
        </salesCommissionsFindersFees>
        <useOfProceeds>
            <grossProceedsUsed>
                <dollarAmount>0</dollarAmount>
            </grossProceedsUsed>
            <clarificationOfResponse></clarificationOfResponse>
        </useOfProceeds>
        <signatureBlock>
            <authorizedRepresentative>false</authorizedRepresentative>
            <signature>
                <issuerName>Keystone Long Only Fund</issuerName>
                <signatureName>KENNETH WILLIAM TONKINSON</signatureName>
                <nameOfSigner>KENNETH WILLIAM TONKINSON</nameOfSigner>
                <signatureTitle>AUTHORIZED SIGNATORY</signatureTitle>
                <signatureDate>2026-05-14</signatureDate>
            </signature>
        </signatureBlock>
    </offeringData>
</edgarSubmission>
