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

    <schemaVersion>X0203</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2009-06-05</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000005272</issuerCik>
        <issuerName>AMERICAN INTERNATIONAL GROUP INC</issuerName>
        <issuerTradingSymbol>AIG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001236615</rptOwnerCik>
            <rptOwnerName>STARR INTERNATIONAL CO INC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>101 BAARERSTRASSE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CH 6300 ZUG</rptOwnerCity>
            <rptOwnerState>V8</rptOwnerState>
            <rptOwnerZipCode>41</rptOwnerZipCode>
            <rptOwnerStateDescription>SWITZERLAND</rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>264561274</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15700000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Footnote</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">These shares are owned directly by Starr International Investments, Ltd., which is a wholly owned subsidiary of Starr International Company, Inc.</footnote>
    </footnotes>

    <remarks>Starr International Company, Inc. may be deemed to beneficially own more than 10% of the common stock of American International Group, Inc. under Rule 16a-1(a)(1) under the Securities Exchange Act of 1934, as amended (the &quot;Exchange Act&quot;), as a result of it being deemed a member of a group under Section 13d(3) of the Exchange Act.</remarks>

    <ownerSignature>
        <signatureName>/s/Mike F. Huang, Attorney-In-Fact</signatureName>
        <signatureDate>2009-06-10</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/Bertil P-H Lundqvist, Attorney-In-Fact</signatureName>
        <signatureDate>2009-06-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
