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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2018-06-21</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001098972</issuerCik>
        <issuerName>AGENUS INC</issuerName>
        <issuerTradingSymbol>AGEN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001744495</rptOwnerCik>
            <rptOwnerName>Cortis Christian</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>3 FORBES ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LEXINGTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02421</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Strategy Officer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>19849</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option, right to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.85</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2016-04-13</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-05-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>85000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option, right to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.16</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2017-03-31</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2026-03-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>50000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option, right to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.77</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2018-03-31</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2027-03-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>60000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option, right to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>5.65</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2019-03-02</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2028-03-02</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Options awarded in accordance with the Agenus Inc. Amended and Restated 2009 Equity Incentive Plan and vests in four equal annual installments beginning April 13, 2016.</footnote>
        <footnote id="F2">Options awarded in accordance with the Agenus Inc. Amended and Restated 2009 Equity Plan and vests in three years with one-third vested on March 31, 2017 and the balance in equal quarterly installments.</footnote>
        <footnote id="F3">Option awarded in accordance with the Agenus Inc. Amended and Restated 2009 Equity Incentive Plan and vests on-third on the one-year anniversary of the grant date, March 31, 2017, with the balance vesting in equal quarterly installments thereafter.</footnote>
        <footnote id="F4">Options was granted on March 2, 2018 subject to shareholder approval, which was obtained at the Company's annual shareholder meeting on June 20, 2018.  Option awarded in accordance with the Agenus Inc. Amended and Restated 2009 Equity Incentive Plan, and vests over three years with one-third of the award vesting on March 2, 2019 and the balance vesting in equal quarterly installments thereafter.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Christine M. Klaskin, by Power of Attorney</signatureName>
        <signatureDate>2018-06-22</signatureDate>
    </ownerSignature>
</ownershipDocument>
