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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-01-01</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000891103</issuerCik>
        <issuerName>IAC/INTERACTIVECORP</issuerName>
        <issuerTradingSymbol>IACI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001238039</rptOwnerCik>
            <rptOwnerName>MCINERNEY THOMAS</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IAC/INTERACTIVECORP</rptOwnerStreet1>
            <rptOwnerStreet2>152 WEST 57TH STREET, 42ND FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10019</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>EVP &amp; CFO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12193</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>467</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Co-Executor &amp; Co-Beneficiary of Estate</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>24.33</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2000-06-23</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2009-06-23</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>140734</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>42.11</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2000-12-27</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2009-12-27</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>121550</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
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                <value>Stock Option (Right to Buy)</value>
                <footnoteId id="F2"/>
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            <conversionOrExercisePrice>
                <value>26.80</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-03-31</value>
                <footnoteId id="F5"/>
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            <expirationDate>
                <value>2010-03-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>70125</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
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            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-05-10</value>
                <footnoteId id="F6"/>
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            <expirationDate>
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            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>15000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
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                    <value>D</value>
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            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
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                <footnoteId id="F2"/>
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            <conversionOrExercisePrice>
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            <exerciseDate>
                <value>2005-02-21</value>
                <footnoteId id="F7"/>
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            <expirationDate>
                <value>2011-02-21</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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            </underlyingSecurity>
            <ownershipNature>
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        </derivativeHolding>
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            <exerciseDate>
                <value>2001-12-31</value>
                <footnoteId id="F8"/>
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            <expirationDate>
                <value>2001-05-15</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>28050</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
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            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2002-12-16</value>
                <footnoteId id="F9"/>
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            <expirationDate>
                <value>2011-12-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>70000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>29.83</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-03-19</value>
                <footnoteId id="F10"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-03-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>3352</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>29.83</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-03-19</value>
                <footnoteId id="F11"/>
            </exerciseDate>
            <expirationDate>
                <value>2012-03-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>10673</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to Buy)</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>29.83</value>
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            <exerciseDate>
                <value>2003-03-19</value>
                <footnoteId id="F12"/>
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            <expirationDate>
                <value>2012-03-19</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>32725</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F13"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2006-01-17</value>
                <footnoteId id="F13"/>
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            <expirationDate>
                <value>2006-01-17</value>
                <footnoteId id="F13"/>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>50000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F14"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-02-04</value>
                <footnoteId id="F14"/>
            </exerciseDate>
            <expirationDate>
                <value>2009-02-04</value>
                <footnoteId id="F14"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>55682</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F15"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
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            <exerciseDate>
                <value>2009-02-04</value>
                <footnoteId id="F15"/>
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            <expirationDate>
                <value>2009-02-04</value>
                <footnoteId id="F15"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>65509</value>
                </underlyingSecurityShares>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes 7,393 shares of IAC Common Stock acquired by the reporting person pursuant to the Company's Bonus Stock Purchase Plan in February 2004.</footnote>
        <footnote id="F2">Received in the merger among the Company, Ticketmaster and T Merger Corp., which was completed on January 17, 2003 (the &quot;Merger&quot;), in exchange for options to purchase common stock of Ticketmaster (the &quot;Ticketmaster Options&quot;).  The vesting of unvested Ticketmaster Options was not accelerated as a result of the Merger and IAC/InterActiveCorp options received in exchange for Ticketmaster Options have substantially the same terms and conditions (including vesting) as were applicable in the case of the related Ticketmaster Options.</footnote>
        <footnote id="F3">Vested in four equal installments on the first, second, third and fourth anniversaries of the grant date (June 23, 1999).</footnote>
        <footnote id="F4">Vested in four equal installments on the first, second, third and fourth anniversaries of the grant date (December 27, 1999).</footnote>
        <footnote id="F5">Vested in four equal installments on the first, second, third and fourth anniversaries of the grant date (March 31, 2000).</footnote>
        <footnote id="F6">Represents stock options granted pursuant to the Company's 1997 Stock &amp; Annual Incentive Plan, which vested in four equal installments on the first, second, third and fourth anniversaries of the grant date (May 10, 2000).</footnote>
        <footnote id="F7">Vests on the fourth anniversary of the grant date (February 21, 2001).</footnote>
        <footnote id="F8">25% vested on December 31, 2001 and the remainder vested in equal installments every six months thereafter.</footnote>
        <footnote id="F9">Represents stock options received pursuant to the Company's 2000 Stock &amp; Annual Incentive Plan, which vest in four equal installments on the first, second, third and fourth anniversaries of the grant date (December 16, 2001).</footnote>
        <footnote id="F10">Vests on the fourth anniversary of the grant date (March 19, 2002).</footnote>
        <footnote id="F11">33% vests on the first, second and third anniversaries of the grant date (March 19, 2002) and the remainder vests on the fourth anniversary of the grant date.</footnote>
        <footnote id="F12">Vests in four equal installments on the first, second, third and fourth anniversaries of the grant date (March 19, 2002).</footnote>
        <footnote id="F13">Represents restricted stock units granted pursuant to the Company's 2000 Stock &amp; Annual Incentive Plan, which vest in one lump sum installment on the third anniversary of the grant date (January 17, 2003).</footnote>
        <footnote id="F14">Represents restricted stock units granted pursuant to the Company's 2000 Stock &amp; Annual Incentive Plan, which vest in equal installments over five years on the anniversary of the grant date (February 4, 2004).</footnote>
        <footnote id="F15">Represents restricted stock units granted pursuant to the Company's 2000 Stock &amp; Annual Incentive Plan, which vest in one lump sum installment on the fifth anniversary of the grant date (February 4, 2004).</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Thomas McInerney</signatureName>
        <signatureDate>2005-01-10</signatureDate>
    </ownerSignature>
</ownershipDocument>

