FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * USHER THOMAS J   2. Issuer Name and Ticker or Trading Symbol MARATHON OIL CORP [MRO] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MARATHON OIL CORPORATION, 5555 SAN FELIPE ROAD 3. Date of Earliest Transaction (Month/Day/Year) 05/10/2005 (Street) HOUSTON, TX 77056 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price COMMON STOCK 05/10/2005   M   175,500 A $ 34 180,512.15 D   COMMON STOCK 05/10/2005   S   175,500 D $ 49.1 (1) 5,012.15 D   COMMON STOCK 05/10/2005   M   325,000 A $ 32.52 330,012.15 D   COMMON STOCK 05/10/2005   S   325,000 D $ 49.1 (1) 5,012.15 D   COMMON STOCK               11,009 I Revocable Trust (2)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

EMPLOYEE STOCK OPTION (Right to Buy)

$ 34

05/10/2005

M(3)

175,500

05/26/1999

05/26/2008

COMMON STOCK

175,500

$ 0

0

D

STOCK APPRECIATION RIGHT

$ 34

05/10/2005

M(3)

175,500

05/26/1999

05/26/2008

COMMON STOCK

175,500

$ 0

0

D

EMPLOYEE STOCK OPTION (Right to Buy)

$ 32.52

05/10/2005

M(3)

325,000

05/29/2002

05/29/2011

COMMON STOCK

325,000

$ 0

0

D

STOCK APPRECIATION RIGHT

$ 32.52

05/10/2005

M(3)

325,000

05/29/2002

05/29/2011

COMMON STOCK

325,000

$ 0

0

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
USHER THOMAS J C/O MARATHON OIL CORPORATION 5555 SAN FELIPE ROAD HOUSTON, TX 77056	X

Signatures

By: R. J. Kolencik, Attorney-in-Fact for Thomas J. Usher		05/11/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Under the terms of the Stock Appreciation Right, the Stock Appreciation Right price is the highest fair market value of Marathon Oil Corporation Common Stock during the ten day trading period commencing May 3, 2005. If the highest fair market value at the end of the ten day trading period exceeds $49.10, the highest fair market value as of the date the reporting person exercised, an amended Form 4 will be filed to reflect the highest fair market value.
(2)	Revocable Trust Account governed by the Revocable Trust Agreement, dated July 3, 2001, pursuant to which the reporting person is the settlor, co-trustee with his spouse and beneficial owner of the shares held in said account.
(3)	Exercise of tandem SAR and cancellation of underlying stock option.

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