-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 L91BPSXcO5pqTW9l7jiXSfTP9xe5zIQHGfju9Wcf5J8iu5x1JSdExQjoNVCBgynW
 b1QHBkDoN/d41nfgH2Sqlg==

<SEC-DOCUMENT>0001179110-05-022356.txt : 20051205
<SEC-HEADER>0001179110-05-022356.hdr.sgml : 20051205
<ACCEPTANCE-DATETIME>20051205162738
ACCESSION NUMBER:		0001179110-05-022356
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20051201
FILED AS OF DATE:		20051205
DATE AS OF CHANGE:		20051205

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JENNINGS STEPHEN M
		CENTRAL INDEX KEY:			0001197694

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-24786
		FILM NUMBER:		051244521

	MAIL ADDRESS:	
		STREET 1:		LTX CORPORATION
		STREET 2:		UNIVERSITY AVE
		CITY:			WESTWOOD
		STATE:			MA
		ZIP:			02090

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ASPEN TECHNOLOGY INC /DE/
		CENTRAL INDEX KEY:			0000929940
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER PROGRAMMING SERVICES [7371]
		IRS NUMBER:				042739697
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		TEN CANAL PARK
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02141
		BUSINESS PHONE:		6179491000

	MAIL ADDRESS:	
		STREET 1:		TEN CANAL PARK
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02141
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-12-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000929940</issuerCik>
        <issuerName>ASPEN TECHNOLOGY INC /DE/</issuerName>
        <issuerTradingSymbol>AZPN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001197694</rptOwnerCik>
            <rptOwnerName>JENNINGS STEPHEN M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ASPEN TECHNOLOGY, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>10 CANAL PARK</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02143</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option to purchase common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.40</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-12-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>6000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>7.40</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-12-01</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-11-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>6000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The option is immediately exercisable in full.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Charles F. Kane, Attorney-in-fact</signatureName>
        <signatureDate>2005-12-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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