<PAGE>
       AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MAY 1, 2003
                                                    REGISTRATION NO. ___________

================================================================================


                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                 -------------

                                    FORM S-8
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                                 -------------

                            MARATHON OIL CORPORATION
             (Exact name of registrant as specified in its charter)

                DELAWARE                                     25-0996816
    (State or other jurisdiction of                       (I.R.S. Employer
     incorporation or organization)                      Identification No.)

          5555 SAN FELIPE ROAD
             HOUSTON, TEXAS                                   77056-2723
(Address of Principal Executive Offices)                       (Zip Code)

            MARATHON OIL CORPORATION 2003 INCENTIVE COMPENSATION PLAN
                            (Full title of the plan)

                          WILLIAM F. SCHWIND, JR., ESQ.
                   VICE PRESIDENT, GENERAL COUNSEL & SECRETARY
                              5555 SAN FELIPE ROAD
                            HOUSTON, TEXAS 77056-2723
                     (Name and address of agent for service)

   Telephone number, including area code, of agent for service: (713) 629-6600

                                 -------------

                                    COPY TO:
                              R. JOEL SWANSON, ESQ.
                               BAKER BOTTS L.L.P.
                              3000 ONE SHELL PLAZA
                                  910 LOUISIANA
                            HOUSTON, TEXAS 77002-4995
                                 (713) 229-1330
                               FAX: (713) 229-1522

                                 -------------

                         CALCULATION OF REGISTRATION FEE

<Table>
<Caption>
=================================================================================================================
                                                                  PROPOSED         PROPOSED
                                                                   MAXIMUM         MAXIMUM
                                                                  OFFERING        AGGREGATE            AMOUNT OF
          TITLE OF SECURITIES                 AMOUNT TO BE          PRICE          OFFERING          REGISTRATION
           TO BE REGISTERED                   REGISTERED(1)       PER SHARE         PRICE                 FEE
-----------------------------------------------------------------------------------------------------------------
<S>                                         <C>                   <C>            <C>                 <C>
Common Stock, $1.00 par value per share     20,000,000 shares     $22.665(2)     $453,300,000(2)       $36,672(2)
-----------------------------------------------------------------------------------------------------------------
</Table>

(1)  Pursuant to Rule 416 under the Securities Act of 1933, as amended (the
     "Securities Act"), this Registration Statement also covers an indeterminate
     number of shares of Common Stock that may be offered or issued by reason of
     stock splits, stock dividends or similar transactions or by reason of
     antidilution provisions of the Marathon Oil Corporation 2003 Incentive
     Compensation Plan.

(2)  Estimated solely for the purpose of calculating the registration fee in
     accordance with Rule 457(c) and 457(h)(1) based upon the average of the
     high and low prices of the Common Stock reported on the New York Stock
     Exchange Composite Tape on April 25, 2003. In addition, pursuant to Rule
     457(p) under the Securities Act, the Registrant hereby offsets the
     registration fee required in connection with this Registration Statement by
     (i) $19,808 previously paid by the Registrant in connection with the
     registration of 2,284,684 shares of Common Stock pursuant to the
     Registration Statement on Form S-8 (Registration No. 333-86847) filed with
     the Securities and Exchange Commission (the "SEC") on September 10, 1999
     and (ii) $16,864 previously paid by the Registrant in connection with the
     registration of 2,337,353 shares of Common Stock pursuant to the
     Registration Statement on Form S-8 (Registration No. 333-55902) filed with
     the SEC on February 20, 2001; in each case which have not been issued and
     which have been or will be deregistered pursuant to post-effective
     amendments to such registration statements filed on the date hereof.
     Accordingly, no filing fee is being paid in connection herewith.


<PAGE>


                             INTRODUCTORY STATEMENT

                  Marathon Oil Corporation, formerly known as USX Corporation
(the "Registrant" or the "Company"), is filing this Registration Statement on
Form S-8 relating to its Common Stock, par value $1.00 per share (the "Common
Stock"), issuable pursuant to the terms of the Marathon Oil Corporation 2003
Incentive Compensation Plan.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

                  Note: The document(s) containing the plan information required
by Item 1 of Form S-8 and the statement of availability of registrant
information and any other information required by Item 2 of Form S-8 will be
sent or given to participants as specified by Rule 428 under the Securities Act
of 1933, as amended (the "Securities Act"). In accordance with Rule 428 and the
requirements of Part I of Form S-8, such documents are not being filed with the
Securities and Exchange Commission (the "Commission") either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424 under the Securities Act. The Registrant shall maintain a file of such
documents in accordance with the provisions of Rule 428. Upon request, the
Registrant shall furnish to the Commission or its staff a copy or copies of all
of the documents included in such file.


                                       1
<PAGE>


                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

                  The following documents filed with the Commission by the
Company (File No. 1-5153) pursuant to the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), or as otherwise indicated, are hereby incorporated
in this Registration Statement by reference and shall be deemed to be a part
hereof:

                  (1) the Company's Annual Report on Form 10-K for the fiscal
         year ended December 31, 2002;

                  (2) the Company's Current Report on Form 8-K dated January 31,
         2003, as filed with the Commission on January 31, 2003;

                  (3) the description of the Common Stock contained in the
         Company's Current Report on Form 8-K dated April 21, 2003, as filed
         with the Commission on April 21, 2003, as that description may be
         updated from time to time; and

                  All documents filed with the Commission by the Company
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act subsequent
to the filing of this Registration Statement and prior to the filing of a
post-effective amendment to this Registration Statement which indicates that all
securities offered hereby have been sold, or which deregisters all securities
then remaining unsold, shall be deemed to be incorporated by reference in this
Registration Statement and to be a part hereof from the date of filing of such
documents.

                  Any statement contained herein or incorporated by reference
herein shall be deemed to be modified or superseded for purposes of this
Registration Statement to the extent that a statement contained herein or in any
subsequently filed document which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

ITEM 4. DESCRIPTION OF SECURITIES.

                  Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

                  Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

Delaware General Corporation Law

                  Section 145 of the Delaware General Corporation Law (the
"DGCL") empowers a Delaware corporation to indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he or she is or was a director or officer, employee or
agent of the corporation, or is or was serving at the request of the corporation
as a director, officer, employee or agent of another corporation, partnership,
joint venture, trust or other enterprise. The indemnity may include expenses
(including attorneys' fees), judgments, fines and amounts paid in settlement
actually and reasonably incurred by that person in connection with such action,
suit or proceeding, provided that such person acted in good faith and in a
manner he or she reasonably believed to be in or not opposed to the best
interests of the

                                       2
<PAGE>


corporation and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his or her conduct was unlawful. A Delaware
corporation may indemnify directors, officers, employees and others against
expenses (including attorneys' fees) in an action by or in the right of the
corporation under the same conditions, except that no indemnification is
permitted without judicial approval if the person to be indemnified has been
adjudged to be liable to the corporation. Where a director or an officer is
successful on the merits or otherwise in the defense of any action referred to
above or in defense of any claim, issue or matter therein, the corporation must
indemnify that director or officer against the expenses (including attorneys'
fees) which he or she actually and reasonably incurred in connection therewith.

                  Section 102(b)(7) of the DGCL provides that a certificate of
incorporation may contain a provision eliminating or limiting the personal
liability of a director to the corporation or its stockholders for monetary
damages for breach of fiduciary duty as a director, provided that such provision
shall not eliminate or limit the liability of a director (1) for any breach of
the director's duty of loyalty to the corporation or its stockholders, (2) for
acts or omissions not in good faith or which involve intentional misconduct or a
knowing violation of law, (3) under Section 174 of the DGCL, or (4) for any
transaction from which the director derived an improper personal benefit.

Certificate of Incorporation and Bylaws

                  Article Eleventh of the Company's restated certificate of
incorporation states that:

                           No director shall be personally liable to the
                 Corporation or its stockholders for monetary damages for any
                 breach of fiduciary duty by such director as a director, except
                 (i) for any breach of the director's duty of loyalty to the
                 Corporation or its stockholders, (ii) for acts or omissions not
                 in good faith or which involve intentional misconduct or a
                 knowing violation of law, (iii) pursuant to Section 174 of the
                 Delaware General Corporation Law, or (iv) for any transaction
                 from which the director derived an improper personal benefit.
                 No amendment to or repeal of this Article Eleventh shall apply
                 to or have any effect on the liability or alleged liability of
                 any director of the Corporation for or with respect to any acts
                 or omissions of such director occurring prior to such amendment
                 or repeal.

                  In addition, Article V of the Company's by-laws provides that
the Company shall indemnify and hold harmless to the fullest extent permitted by
law any person who was or is made or is threatened to be made a party or is
involved in any action, suit or proceeding, whether civil, criminal,
administrative or investigative, by reason of the fact that such person is or
was a director, officer, employee or agent of the Company or is or was serving
at the request of the Company as an officer, director, employee or agent of
another corporation, partnership, joint venture, trust, enterprise or nonprofit
entity, including service with respect to employee benefit plans, against all
expenses, liability and loss reasonably incurred or suffered by such person. The
Company shall indemnify any person seeking indemnity in connection with a
proceeding initiated by such person only if the proceeding was authorized by the
Company's board of directors.

Indemnification Agreements and Insurance

                  Agreements the Company may enter into with underwriters,
dealers and agents who participate in the distribution of securities of the
Company may contain provisions relating to the indemnification of the Company's
officers and directors.

                  The Company also maintains directors' and officers' liability
insurance for its directors and officers that protects them from certain losses
arising from claims or charges made against them in their capacities as
directors or officers of the Company.

                  The Company maintains insurance policies under which the
Company's directors and officers are insured, within the limits and subject to
the limitations of the policies, against certain expenses in connection with the
defense of actions, suits or proceedings, and certain liabilities which might be
imposed as a result of such actions, suits or proceedings, to which they are
parties by reason of being or having been such directors or officers.


                                       3
<PAGE>


ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

                  Not Applicable.

ITEM 8. EXHIBITS.

                  The following documents are filed as a part of this
Registration Statement or incorporated by reference herein:

<Table>
<Caption>

EXHIBIT
NUMBER                       DESCRIPTION OF EXHIBIT
------                       ----------------------
<S>      <C>
4.1      Restated Certificate of Incorporation (incorporated by reference herein
         to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the
         year ended December 31, 2001 (File No. 1-05153)).

4.2      By-laws (incorporated by reference herein to Exhibit 3(b) to the
         Company's Annual Report on Form 10-K for the year ended December 31,
         2002 (File No. 1-05153)).

4.3      Specimen of Common Stock certificate (incorporated by reference herein
         to Exhibit 4.3 to the Company's Registration Statement on Form S-3
         (Reg. No. 333-88797)).

4.4      Form of Marathon Oil Corporation 2003 Incentive Compensation Plan
         (incorporated by reference herein to Appendix C of the Company's
         Notice of Annual Meeting of Stockholders and Proxy Statement 2003 dated
         March 10, 2003).

*5.1     Opinion of Baker Botts L.L.P.

*23.1    Consent of PricewaterhouseCoopers LLP.

*23.2    Consent of Baker Botts L.L.P. (included in Exhibit 5.1).

*24.1    Powers of Attorney.
</Table>

---------

*  Filed herewith.


                                       4
<PAGE>


ITEM 9. UNDERTAKINGS.

                  (a) The undersigned registrant hereby undertakes:

                           (1) To file, during any period in which offers or
         sales are being made, a post-effective amendment to this registration
         statement:

                                    (i) To include any prospectus required by
                           section 10(a)(3) of the Securities Act;

                                    (ii) To reflect in the prospectus any facts
                           or events arising after the effective date of the
                           registration statement (or the most recent
                           post-effective amendment thereof) which, individually
                           or in the aggregate, represent a fundamental change
                           in the information set forth in the registration
                           statement. Notwithstanding the foregoing, any
                           increase or decrease in volume of securities offered
                           (if the total dollar value of securities offered
                           would not exceed that which was registered) and any
                           deviation from the low or high end of the estimated
                           maximum offering range may be reflected in the form
                           of prospectus filed with the Commission pursuant to
                           Rule 424(b) of the Securities Act if, in the
                           aggregate, the changes in volume and price represent
                           no more than a 20% change in the maximum aggregate
                           offering price set forth in the "Calculation of
                           Registration Fee" table in the effective registration
                           statement;

                                    (iii) To include any material information
                           with respect to the plan of distribution not
                           previously disclosed in the registration statement or
                           any material change to such information in the
                           registration statement;

                           Provided, however, that the undertakings set forth in
                  paragraphs (i) and (ii) above do not apply if the registration
                  statement is on Form S-3 or Form S-8, and the information
                  required to be included in a post-effective amendment by those
                  paragraphs is contained in periodic reports filed with or
                  furnished to the Commission by the registrant pursuant to
                  Section 13 or Section 15(d) of the Exchange Act that are
                  incorporated by reference in the registration statement.

                           (2) That, for the purpose of determining any
                  liability under the Securities Act, each such post-effective
                  amendment shall be deemed to be a new registration statement
                  relating to the securities offered therein, and the offering
                  of such securities at that time shall be deemed to be the
                  initial bona fide offering thereof.

                           (3) To remove from registration by means of a
                  post-effective amendment any of the securities being
                  registered which remain unsold at the termination of the
                  offering.

                  (b) The undersigned registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act, each filing of
the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  (c) Insofar as indemnification for liabilities arising under
the Securities Act may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the registrant of expenses
incurred or paid by a director, officer or controlling person of the registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.


                                       5
<PAGE>


                                   SIGNATURES


                  Pursuant to the requirements of the Securities Act of 1933,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Houston, the State of Texas, on May 1, 2003.


                                       MARATHON OIL CORPORATION
                                       (Registrant)



                                       By:   /s/ Clarence P. Cazalot, Jr.
                                          --------------------------------------
                                                 Clarence P. Cazalot, Jr.
                                           President and Chief Executive Officer



                  Pursuant to the requirements of the Securities Act of 1933,
this Registration Statement has been signed by the following persons in the
capacities and on May 1, 2003.


<Table>
<Caption>
        SIGNATURE                                 TITLE
        ---------                                 -----
<S>                                <C>
/s/ Clarence P. Cazalot, Jr.       President, Chief Executive Officer and
----------------------------       Director (Principal Executive Officer)
    Clarence P. Cazalot, Jr.

   /s/ John T. Mills                      Chief Financial Officer
----------------------------           (Principal Financial Officer)
       John T. Mills

  /s/ Albert G. Adkins             Vice President-Accounting and Controller
----------------------------            (Principal Accounting Officer)
      Albert G. Adkins


/s/ Charles F. Bolden, Jr.*                     Director
----------------------------
    Charles F. Bolden, Jr.



   /s/ David A. Daberko*                        Director
----------------------------
     David A. Daberko



   /s/ William L. Davis*                        Director
----------------------------
     William L. Davis
</Table>



                                       6
<PAGE>


<Table>
<Caption>
        SIGNATURE                                 TITLE
        ---------                                 -----
<S>                                <C>
/s/ Dr. Shirley Ann Jackson*                    Director
----------------------------
  Dr. Shirley Ann Jackson



     /s/ Philip Lader*                          Director
----------------------------
       Philip Lader


    /s/ Charles R. Lee*                         Director
----------------------------
      Charles R. Lee



   /s/ Dennis H. Reilley*                       Director
----------------------------
     Dennis H. Reilley



   /s/ Seth E. Schofield*                       Director
----------------------------
     Seth E. Schofield



     /s/ Thomas J. Usher*               Chairman of the Board
----------------------------
       Thomas J. Usher



   /s/ Douglas C. Yearley*                      Director
----------------------------
     Douglas C. Yearley



*By: /s/ John T. Mills
    -----------------------
         John T. Mills
       Attorney in Fact
</Table>


                                       7
<PAGE>


                                INDEX TO EXHIBITS


<Table>
<Caption>
EXHIBIT
NUMBER                       DESCRIPTION OF EXHIBIT
------                       ----------------------
<S>      <C>
4.1      Restated Certificate of Incorporation (incorporated by reference herein
         to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the
         year ended December 31, 2001 (File No. 1-05153)).

4.2      By-laws (incorporated by reference herein to Exhibit 3(b) to the
         Company's Annual Report on Form 10-K for the year ended December 31,
         2002 (File No. 1-05153)).

4.3      Specimen of Common Stock certificate (incorporated by reference herein
         to Exhibit 4.3 to the Company's Registration Statement on Form S-3
         (Reg. No. 333-88797)).

4.4      Form of Marathon Oil Corporation 2003 Incentive Compensation Plan
         (incorporated by reference herein to Appendix C of the Company's Notice
         of Annual Meeting of Stockholders and Proxy Statement 2003 dated March
         10, 2003).

*5.1     Opinion of Baker Botts L.L.P.

*23.1    Consent of PricewaterhouseCoopers LLP.

*23.2    Consent of Baker Botts L.L.P. (included in Exhibit 5.1).

*24.1    Powers of Attorney.
</Table>

---------

*  Filed herewith.


                                       8
[{"type": "S-8", "sequence": "1", "filename": "h05341sv8.txt", "description": "MARATHON OIL CORPORATION", "secsgml_size_bytes": 26025}]
{"company-data": {"conformed-name": "MARATHON OIL CORP", "cik": "0000101778", "assigned-sic": "2911", "irs-number": "250996816", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-104910", "film-number": "03677308"}, "business-address": {"street1": "P O BOX 3128", "city": "HOUSTON", "state": "TX", "zip": "77253-3128", "phone": "7136296600"}, "former-company": [{"former-conformed-name": "UNITED STATES STEEL CORP/DE", "date-changed": "19860714"}, {"former-conformed-name": "USX CORP", "date-changed": "19920703"}]}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON MAY 1, 2003
                                                    REGISTRATION NO. ___________

================================================================================

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                 -------------

                                    FORM S-8
             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                                 -------------

                            MARATHON OIL CORPORATION
             (Exact name of registrant as specified in its charter)

                DELAWARE                                     25-0996816
    (State or other jurisdiction of                       (I.R.S. Employer
     incorporation or organization)                      Identification No.)

          5555 SAN FELIPE ROAD
             HOUSTON, TEXAS                                   77056-2723
(Address of Principal Executive Offices)                       (Zip Code)

            MARATHON OIL CORPORATION 2003 INCENTIVE COMPENSATION PLAN
                            (Full title of the plan)

                          WILLIAM F. SCHWIND, JR., ESQ.
                   VICE PRESIDENT, GENERAL COUNSEL & SECRETARY
                              5555 SAN FELIPE ROAD
                            HOUSTON, TEXAS 77056-2723
                     (Name and address of agent for service)

   Telephone number, including area code, of agent for service: (713) 629-6600

                                 -------------

                                    COPY TO:
                              R. JOEL SWANSON, ESQ.
                               BAKER BOTTS L.L.P.
                              3000 ONE SHELL PLAZA
                                  910 LOUISIANA
                            HOUSTON, TEXAS 77002-4995
                                 (713) 229-1330
                               FAX: (713) 229-1522

                                 -------------

                         CALCULATION OF REGISTRATION FEE
=================================================================================================================
                                                                  PROPOSED         PROPOSED
                                                                   MAXIMUM         MAXIMUM
                                                                  OFFERING        AGGREGATE            AMOUNT OF
          TITLE OF SECURITIES                 AMOUNT TO BE          PRICE          OFFERING          REGISTRATION
           TO BE REGISTERED                   REGISTERED(1)       PER SHARE         PRICE                 FEE
-----------------------------------------------------------------------------------------------------------------
Common Stock, $1.00 par value per share     20,000,000 shares     $22.665(2)     $453,300,000(2)       $36,672(2)
-----------------------------------------------------------------------------------------------------------------
(1)  Pursuant to Rule 416 under the Securities Act of 1933, as amended (the
     "Securities Act"), this Registration Statement also covers an indeterminate
     number of shares of Common Stock that may be offered or issued by reason of
     stock splits, stock dividends or similar transactions or by reason of
     antidilution provisions of the Marathon Oil Corporation 2003 Incentive
     Compensation Plan.

(2)  Estimated solely for the purpose of calculating the registration fee in
     accordance with Rule 457(c) and 457(h)(1) based upon the average of the
     high and low prices of the Common Stock reported on the New York Stock
     Exchange Composite Tape on April 25, 2003. In addition, pursuant to Rule
     457(p) under the Securities Act, the Registrant hereby offsets the
     registration fee required in connection with this Registration Statement by
     (i) $19,808 previously paid by the Registrant in connection with the
     registration of 2,284,684 shares of Common Stock pursuant to the
     Registration Statement on Form S-8 (Registration No. 333-86847) filed with
     the Securities and Exchange Commission (the "SEC") on September 10, 1999
     and (ii) $16,864 previously paid by the Registrant in connection with the
     registration of 2,337,353 shares of Common Stock pursuant to the
     Registration Statement on Form S-8 (Registration No. 333-55902) filed with
     the SEC on February 20, 2001; in each case which have not been issued and
     which have been or will be deregistered pursuant to post-effective
     amendments to such registration statements filed on the date hereof.
     Accordingly, no filing fee is being paid in connection herewith.
INTRODUCTORY STATEMENT

                  Marathon Oil Corporation, formerly known as USX Corporation
(the "Registrant" or the "Company"), is filing this Registration Statement on
Form S-8 relating to its Common Stock, par value $1.00 per share (the "Common
Stock"), issuable pursuant to the terms of the Marathon Oil Corporation 2003
Incentive Compensation Plan.

                                     PART I

              INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

                  Note: The document(s) containing the plan information required
by Item 1 of Form S-8 and the statement of availability of registrant
information and any other information required by Item 2 of Form S-8 will be
sent or given to participants as specified by Rule 428 under the Securities Act
of 1933, as amended (the "Securities Act"). In accordance with Rule 428 and the
requirements of Part I of Form S-8, such documents are not being filed with the
Securities and Exchange Commission (the "Commission") either as part of this
Registration Statement or as prospectuses or prospectus supplements pursuant to
Rule 424 under the Securities Act. The Registrant shall maintain a file of such
documents in accordance with the provisions of Rule 428. Upon request, the
Registrant shall furnish to the Commission or its staff a copy or copies of all
of the documents included in such file.

                                       1
PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

                  The following documents filed with the Commission by the
Company (File No. 1-5153) pursuant to the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), or as otherwise indicated, are hereby incorporated
in this Registration Statement by reference and shall be deemed to be a part
hereof:

                  (1) the Company's Annual Report on Form 10-K for the fiscal
         year ended December 31, 2002;

                  (2) the Company's Current Report on Form 8-K dated January 31,
         2003, as filed with the Commission on January 31, 2003;

                  (3) the description of the Common Stock contained in the
         Company's Current Report on Form 8-K dated April 21, 2003, as filed
         with the Commission on April 21, 2003, as that description may be
         updated from time to time; and

                  All documents filed with the Commission by the Company
pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act subsequent
to the filing of this Registration Statement and prior to the filing of a
post-effective amendment to this Registration Statement which indicates that all
securities offered hereby have been sold, or which deregisters all securities
then remaining unsold, shall be deemed to be incorporated by reference in this
Registration Statement and to be a part hereof from the date of filing of such
documents.

                  Any statement contained herein or incorporated by reference
herein shall be deemed to be modified or superseded for purposes of this
Registration Statement to the extent that a statement contained herein or in any
subsequently filed document which also is or is deemed to be incorporated by
reference herein modifies or supersedes such statement. Any statement so
modified or superseded shall not be deemed, except as so modified or superseded,
to constitute a part of this Registration Statement.

ITEM 4. DESCRIPTION OF SECURITIES.

                  Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

                  Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

Delaware General Corporation Law

                  Section 145 of the Delaware General Corporation Law (the
"DGCL") empowers a Delaware corporation to indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he or she is or was a director or officer, employee or
agent of the corporation, or is or was serving at the request of the corporation
as a director, officer, employee or agent of another corporation, partnership,
joint venture, trust or other enterprise. The indemnity may include expenses
(including attorneys' fees), judgments, fines and amounts paid in settlement
actually and reasonably incurred by that person in connection with such action,
suit or proceeding, provided that such person acted in good faith and in a
manner he or she reasonably believed to be in or not opposed to the best
interests of the

                                       2
corporation and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his or her conduct was unlawful. A Delaware
corporation may indemnify directors, officers, employees and others against
expenses (including attorneys' fees) in an action by or in the right of the
corporation under the same conditions, except that no indemnification is
permitted without judicial approval if the person to be indemnified has been
adjudged to be liable to the corporation. Where a director or an officer is
successful on the merits or otherwise in the defense of any action referred to
above or in defense of any claim, issue or matter therein, the corporation must
indemnify that director or officer against the expenses (including attorneys'
fees) which he or she actually and reasonably incurred in connection therewith.

                  Section 102(b)(7) of the DGCL provides that a certificate of
incorporation may contain a provision eliminating or limiting the personal
liability of a director to the corporation or its stockholders for monetary
damages for breach of fiduciary duty as a director, provided that such provision
shall not eliminate or limit the liability of a director (1) for any breach of
the director's duty of loyalty to the corporation or its stockholders, (2) for
acts or omissions not in good faith or which involve intentional misconduct or a
knowing violation of law, (3) under Section 174 of the DGCL, or (4) for any
transaction from which the director derived an improper personal benefit.

Certificate of Incorporation and Bylaws

                  Article Eleventh of the Company's restated certificate of
incorporation states that:

                           No director shall be personally liable to the
                 Corporation or its stockholders for monetary damages for any
                 breach of fiduciary duty by such director as a director, except
                 (i) for any breach of the director's duty of loyalty to the
                 Corporation or its stockholders, (ii) for acts or omissions not
                 in good faith or which involve intentional misconduct or a
                 knowing violation of law, (iii) pursuant to Section 174 of the
                 Delaware General Corporation Law, or (iv) for any transaction
                 from which the director derived an improper personal benefit.
                 No amendment to or repeal of this Article Eleventh shall apply
                 to or have any effect on the liability or alleged liability of
                 any director of the Corporation for or with respect to any acts
                 or omissions of such director occurring prior to such amendment
                 or repeal.

                  In addition, Article V of the Company's by-laws provides that
the Company shall indemnify and hold harmless to the fullest extent permitted by
law any person who was or is made or is threatened to be made a party or is
involved in any action, suit or proceeding, whether civil, criminal,
administrative or investigative, by reason of the fact that such person is or
was a director, officer, employee or agent of the Company or is or was serving
at the request of the Company as an officer, director, employee or agent of
another corporation, partnership, joint venture, trust, enterprise or nonprofit
entity, including service with respect to employee benefit plans, against all
expenses, liability and loss reasonably incurred or suffered by such person. The
Company shall indemnify any person seeking indemnity in connection with a
proceeding initiated by such person only if the proceeding was authorized by the
Company's board of directors.

Indemnification Agreements and Insurance

                  Agreements the Company may enter into with underwriters,
dealers and agents who participate in the distribution of securities of the
Company may contain provisions relating to the indemnification of the Company's
officers and directors.

                  The Company also maintains directors' and officers' liability
insurance for its directors and officers that protects them from certain losses
arising from claims or charges made against them in their capacities as
directors or officers of the Company.

                  The Company maintains insurance policies under which the
Company's directors and officers are insured, within the limits and subject to
the limitations of the policies, against certain expenses in connection with the
defense of actions, suits or proceedings, and certain liabilities which might be
imposed as a result of such actions, suits or proceedings, to which they are
parties by reason of being or having been such directors or officers.

                                       3
ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

                  Not Applicable.

ITEM 8. EXHIBITS.

                  The following documents are filed as a part of this
Registration Statement or incorporated by reference herein:
EXHIBIT
NUMBER                       DESCRIPTION OF EXHIBIT
------                       ----------------------
4.1      Restated Certificate of Incorporation (incorporated by reference herein
         to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the
         year ended December 31, 2001 (File No. 1-05153)).

4.2      By-laws (incorporated by reference herein to Exhibit 3(b) to the
         Company's Annual Report on Form 10-K for the year ended December 31,
         2002 (File No. 1-05153)).

4.3      Specimen of Common Stock certificate (incorporated by reference herein
         to Exhibit 4.3 to the Company's Registration Statement on Form S-3
         (Reg. No. 333-88797)).

4.4      Form of Marathon Oil Corporation 2003 Incentive Compensation Plan
         (incorporated by reference herein to Appendix C of the Company's
         Notice of Annual Meeting of Stockholders and Proxy Statement 2003 dated
         March 10, 2003).

*5.1     Opinion of Baker Botts L.L.P.

*23.1    Consent of PricewaterhouseCoopers LLP.

*23.2    Consent of Baker Botts L.L.P. (included in Exhibit 5.1).

*24.1    Powers of Attorney.
---------

*  Filed herewith.

                                       4
ITEM 9. UNDERTAKINGS.

                  (a) The undersigned registrant hereby undertakes:

                           (1) To file, during any period in which offers or
         sales are being made, a post-effective amendment to this registration
         statement:

                                    (i) To include any prospectus required by
                           section 10(a)(3) of the Securities Act;

                                    (ii) To reflect in the prospectus any facts
                           or events arising after the effective date of the
                           registration statement (or the most recent
                           post-effective amendment thereof) which, individually
                           or in the aggregate, represent a fundamental change
                           in the information set forth in the registration
                           statement. Notwithstanding the foregoing, any
                           increase or decrease in volume of securities offered
                           (if the total dollar value of securities offered
                           would not exceed that which was registered) and any
                           deviation from the low or high end of the estimated
                           maximum offering range may be reflected in the form
                           of prospectus filed with the Commission pursuant to
                           Rule 424(b) of the Securities Act if, in the
                           aggregate, the changes in volume and price represent
                           no more than a 20% change in the maximum aggregate
                           offering price set forth in the "Calculation of
                           Registration Fee" table in the effective registration
                           statement;

                                    (iii) To include any material information
                           with respect to the plan of distribution not
                           previously disclosed in the registration statement or
                           any material change to such information in the
                           registration statement;

                           Provided, however, that the undertakings set forth in
                  paragraphs (i) and (ii) above do not apply if the registration
                  statement is on Form S-3 or Form S-8, and the information
                  required to be included in a post-effective amendment by those
                  paragraphs is contained in periodic reports filed with or
                  furnished to the Commission by the registrant pursuant to
                  Section 13 or Section 15(d) of the Exchange Act that are
                  incorporated by reference in the registration statement.

                           (2) That, for the purpose of determining any
                  liability under the Securities Act, each such post-effective
                  amendment shall be deemed to be a new registration statement
                  relating to the securities offered therein, and the offering
                  of such securities at that time shall be deemed to be the
                  initial bona fide offering thereof.

                           (3) To remove from registration by means of a
                  post-effective amendment any of the securities being
                  registered which remain unsold at the termination of the
                  offering.

                  (b) The undersigned registrant hereby undertakes that, for
purposes of determining any liability under the Securities Act, each filing of
the registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) that is
incorporated by reference in this registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

                  (c) Insofar as indemnification for liabilities arising under
the Securities Act may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Commission such
indemnification is against public policy as expressed in the Securities Act and
is, therefore, unenforceable. In the event that a claim for indemnification
against such liabilities (other than the payment by the registrant of expenses
incurred or paid by a director, officer or controlling person of the registrant
in the successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant will, unless in the opinion of its counsel the matter
has been settled by controlling precedent, submit to a court of appropriate
jurisdiction the question whether such indemnification by it is against public
policy as expressed in the Securities Act and will be governed by the final
adjudication of such issue.

                                       5
SIGNATURES

                  Pursuant to the requirements of the Securities Act of 1933,
the Registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
Registration Statement to be signed on its behalf by the undersigned, thereunto
duly authorized, in the City of Houston, the State of Texas, on May 1, 2003.

                                       MARATHON OIL CORPORATION
                                       (Registrant)

                                       By:   /s/ Clarence P. Cazalot, Jr.
                                          --------------------------------------
                                                 Clarence P. Cazalot, Jr.
                                           President and Chief Executive Officer

                  Pursuant to the requirements of the Securities Act of 1933,
this Registration Statement has been signed by the following persons in the
capacities and on May 1, 2003.
SIGNATURE                                 TITLE
        ---------                                 -----
/s/ Clarence P. Cazalot, Jr.       President, Chief Executive Officer and
----------------------------       Director (Principal Executive Officer)
    Clarence P. Cazalot, Jr.

   /s/ John T. Mills                      Chief Financial Officer
----------------------------           (Principal Financial Officer)
       John T. Mills

  /s/ Albert G. Adkins             Vice President-Accounting and Controller
----------------------------            (Principal Accounting Officer)
      Albert G. Adkins

/s/ Charles F. Bolden, Jr.*                     Director
----------------------------
    Charles F. Bolden, Jr.

   /s/ David A. Daberko*                        Director
----------------------------
     David A. Daberko

   /s/ William L. Davis*                        Director
----------------------------
     William L. Davis
6
SIGNATURE                                 TITLE
        ---------                                 -----
/s/ Dr. Shirley Ann Jackson*                    Director
----------------------------
  Dr. Shirley Ann Jackson

     /s/ Philip Lader*                          Director
----------------------------
       Philip Lader

    /s/ Charles R. Lee*                         Director
----------------------------
      Charles R. Lee

   /s/ Dennis H. Reilley*                       Director
----------------------------
     Dennis H. Reilley

   /s/ Seth E. Schofield*                       Director
----------------------------
     Seth E. Schofield

     /s/ Thomas J. Usher*               Chairman of the Board
----------------------------
       Thomas J. Usher

   /s/ Douglas C. Yearley*                      Director
----------------------------
     Douglas C. Yearley

*By: /s/ John T. Mills
    -----------------------
         John T. Mills
       Attorney in Fact
7
INDEX TO EXHIBITS
EXHIBIT
NUMBER                       DESCRIPTION OF EXHIBIT
------                       ----------------------
4.1      Restated Certificate of Incorporation (incorporated by reference herein
         to Exhibit 3(a) to the Company's Annual Report on Form 10-K for the
         year ended December 31, 2001 (File No. 1-05153)).

4.2      By-laws (incorporated by reference herein to Exhibit 3(b) to the
         Company's Annual Report on Form 10-K for the year ended December 31,
         2002 (File No. 1-05153)).

4.3      Specimen of Common Stock certificate (incorporated by reference herein
         to Exhibit 4.3 to the Company's Registration Statement on Form S-3
         (Reg. No. 333-88797)).

4.4      Form of Marathon Oil Corporation 2003 Incentive Compensation Plan
         (incorporated by reference herein to Appendix C of the Company's Notice
         of Annual Meeting of Stockholders and Proxy Statement 2003 dated March
         10, 2003).

*5.1     Opinion of Baker Botts L.L.P.

*23.1    Consent of PricewaterhouseCoopers LLP.

*23.2    Consent of Baker Botts L.L.P. (included in Exhibit 5.1).

*24.1    Powers of Attorney.
---------

*  Filed herewith.

                                       8