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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2026-02-10</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0002091176</issuerCik>
        <issuerName>Idea Acquisition Corp.</issuerName>
        <issuerTradingSymbol>IACO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0002110821</rptOwnerCik>
            <rptOwnerName>Clark Nathan P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IDEA ACQUISITION CORP.</rptOwnerStreet1>
            <rptOwnerStreet2>1010 WILSHIRE BOULEVARD, SUITE 1604</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90017</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <remarks>See Exhibit 24.1 - Power of Attorney.</remarks>

    <ownerSignature>
        <signatureName>/s/ Jordan Leon, Attorney-in-Fact</signatureName>
        <signatureDate>2026-02-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
