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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-04-01</periodOfReport>

    <issuer>
        <issuerCik>0000101594</issuerCik>
        <issuerName>US ENERGY CORP</issuerName>
        <issuerTradingSymbol>USEG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001267115</rptOwnerCik>
            <rptOwnerName>LARSEN MARK J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>877 N 8TH ST W</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>RIVERTON</rptOwnerCity>
            <rptOwnerState>WY</rptOwnerState>
            <rptOwnerZipCode>82501</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>PRESIDENT &amp; COO</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-04-01</value>
            </transactionDate>
            <deemedExecutionDate>
                <value>2008-04-04</value>
            </deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.1</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>132772</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4600</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Custodian For Child</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52272</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>134281</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Immediate Family</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>155811</value>
                    <footnoteId id="F6"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.25</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2002-08-08</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-12-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>52556</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>52556</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.4</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-01-10</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-01-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>41248</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>41248</value>
                    <footnoteId id="F8"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.46</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-07-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>98519</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>98519</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.88</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>1998-12-04</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-09-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>27782</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>27782</value>
                    <footnoteId id="F8"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.86</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-10-14</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-10-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.9</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-12-07</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-12-06</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                    <footnoteId id="F7"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.97</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-01-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2017-07-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>200000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>200000</value>
                    <footnoteId id="F9"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F4">Includes shares held in the U.S. Energy Corp. Employee Stock Ownership Plan (the'ESOP') in an account established for the benefit of the Reporting Person.</footnote>
        <footnote id="F7">Includes stock options granted under the Issuer's 2001 Incentive Stock Option Plan and exempt under Rule 16b-3.</footnote>
        <footnote id="F2">Includes shares held directly by the Reporting Person.</footnote>
        <footnote id="F8">Includes stock options granted under the Issuer's 1998 Incentive Stock Option Plan and exempt under Rule 16b-3.</footnote>
        <footnote id="F9">Stock options granted under the Issuer's 2001 Incentive Stock Option Plan with a 5 year vesting schedule and exempt under Rule 16b-3.</footnote>
        <footnote id="F1">Shares issued to the Reporting Person under the USEG 2001 Stock Compensation Plan. The issuance of these shares is for the funding obligation under the plan for the second quarter of the calendar year ending December 31, 2008. The Issuer has agreed under the terms of the Plan to pay all taxes due. The Reporting Person has agreed not to sell these shares to the market or pledge them on obligations until after his (i) retirement; (ii) total disability or (iii) in the case of the death of the Reporting Person his estate may sell the shares of stock.</footnote>
        <footnote id="F3">Shares indirectly held by the Reporting Person as Custodian for minor children under the Wyoming Uniform Transfers to Minors Act.  The Reporting Person disclaims beneficial and pecuniary interest in these shares.</footnote>
        <footnote id="F5">Includes a balance of shares held in ESOP accounts established to benefit members of the Reporting Persons 'Immediate Family' as that term is defined in Rule 16a-1(e) in accordance with Rule 16a-8(b)(2).</footnote>
        <footnote id="F6">Shares issued to be held in the ESOP which are not allocated to accounts established for the benefit of specific plan participants.  The Reporting Person, as an ESOP Trustee, exercises the voting powers with respect to such unallocated shares.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>MARKJLARSEN</signatureName>
        <signatureDate>2008-04-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2008-04-01
0000101594
US ENERGY CORP
USEG
0001267115
LARSEN MARK J
877 N 8TH ST W
RIVERTON
WY
82501
1
1
0
0
PRESIDENT & COO
Common Stock
2008-04-01
2008-04-04
4
J
0
5000
3.1
A
132772
D
Common Stock
4600
I
By Custodian For Child
Common Stock
52272
I
By ESOP
Common Stock
134281
I
By Immediate Family
Common Stock
155811
I
By Trust
Stock Options (Right to buy)
2.25
2002-08-08
2011-12-07
Common Stock
52556
52556
D
Stock Options (Right to buy)
2.4
2001-01-10
2011-01-09
Common Stock
41248
41248
D
Stock Options (Right to buy)
2.46
2004-07-01
2014-06-30
Common Stock
98519
98519
D
Stock Options (Right to buy)
2.88
1998-12-04
2008-09-05
Common Stock
27782
27782
D
Stock Options (Right to buy)
3.86
2005-10-14
2015-10-13
Common Stock
100000
100000
D
Stock Options (Right to buy)
3.9
2001-12-07
2011-12-06
Common Stock
100000
100000
D
Stock Options (Right to buy)
4.97
2008-01-01
2017-07-26
Common Stock
200000
200000
D
Includes shares held in the U.S. Energy Corp. Employee Stock Ownership Plan (the'ESOP') in an account established for the benefit of the Reporting Person.
Includes stock options granted under the Issuer's 2001 Incentive Stock Option Plan and exempt under Rule 16b-3.
Includes shares held directly by the Reporting Person.
Includes stock options granted under the Issuer's 1998 Incentive Stock Option Plan and exempt under Rule 16b-3.
Stock options granted under the Issuer's 2001 Incentive Stock Option Plan with a 5 year vesting schedule and exempt under Rule 16b-3.
Shares issued to the Reporting Person under the USEG 2001 Stock Compensation Plan. The issuance of these shares is for the funding obligation under the plan for the second quarter of the calendar year ending December 31, 2008. The Issuer has agreed under the terms of the Plan to pay all taxes due. The Reporting Person has agreed not to sell these shares to the market or pledge them on obligations until after his (i) retirement; (ii) total disability or (iii) in the case of the death of the Reporting Person his estate may sell the shares of stock.
Shares indirectly held by the Reporting Person as Custodian for minor children under the Wyoming Uniform Transfers to Minors Act.  The Reporting Person disclaims beneficial and pecuniary interest in these shares.
Includes a balance of shares held in ESOP accounts established to benefit members of the Reporting Persons 'Immediate Family' as that term is defined in Rule 16a-1(e) in accordance with Rule 16a-8(b)(2).
Shares issued to be held in the ESOP which are not allocated to accounts established for the benefit of specific plan participants.  The Reporting Person, as an ESOP Trustee, exercises the voting powers with respect to such unallocated shares.
MARKJLARSEN
2008-04-02