Marathon Oil (MRO)

Proxy and Voting Instruction Form

This Proxy and Voting Instruction is solicited on behalf of the Board of Directors

for the Annual Meeting of Stockholders on April 30, 2008

For shares held by registered holders

The undersigned hereby appoints Thomas J. Usher, Clarence P. Cazalot, Jr. and Janet F. Clark, or any of them, proxies to vote as herein directed on behalf of the undersigned at the Annual Meeting of Stockholders of Marathon Oil Corporation on Wednesday, April 30, 2008 and at any meeting resulting from an adjournment(s) or postponement(s) thereof and upon all other matters properly coming before the Meeting, including the proposals set forth in the 2008 Notice of Annual Meeting and Proxy Statement for such Meeting with respect to which the proxies are instructed to vote as directed on reverse side. You are encouraged to specify your choice by marking the appropriate boxes on the reverse side, but you need not mark any boxes if you wish to vote in accordance with the Board of Directors’ recommendations. The proxies cannot vote your shares unless you sign and return the proxy card.

For shares held in Marathon Oil Company Thrift Plan

These confidential voting instructions are to Fidelity Management Trust Company, as Trustee for the Marathon Oil Company Thrift Plan (the “Marathon Plan”). The undersigned, as a participant in the Marathon Plan, hereby directs the Trustee to vote the number of shares of Marathon Oil Corporation common stock credited to the undersigned’s account under the Marathon Plan at the Annual Meeting of Stockholders, and at any meeting resulting from an adjournment(s) or postponement(s) thereof, upon all subjects that may properly come before the meeting, including the matters described in the 2008 Notice of Annual Meeting and Proxy Statement. In the Trustee’s discretion, it may vote upon such other matters as may properly come before the Meeting. Your vote is confidential. The shares credited to your account will be voted as directed on the reverse side. If no direction is made, if the card is not signed, or if the card is not received by April 27, 2008, the shares credited to your account will not be voted. You cannot vote your shares in person at the Annual Meeting; the Trustee is the only one who can vote your shares.

PROXY TO BE SIGNED AND DATED ON THE REVERSE SIDE