XTO Xto Energy, Inc.

SUMMARY

This summary highlights selected information from this proxy statement/prospectus. It may not contain all of the information that is important to you. You are urged to read carefully the entire proxy statement/prospectus and the other documents referred to in this proxy statement/prospectus in order to fully understand the merger agreement and the proposed merger. See “Where You Can Find More Information” beginning on page 131 of this proxy statement/prospectus. Each item in this summary refers to the page of this proxy statement/prospectus on which that subject is discussed in more detail.

Information about ExxonMobil, XTO Energy and ExxonMobil Investment Corporation (See Page 36).

Exxon Mobil Corporation

Exxon Mobil Corporation, which is referred to in this proxy statement/prospectus as ExxonMobil, was incorporated in the State of New Jersey in 1882. Divisions and affiliated companies of ExxonMobil operate or market products in the United States and most other countries of the world. Their principal business is energy, involving exploration for, and production of, crude oil and natural gas, manufacture of petroleum products and transportation and sale of crude oil, natural gas and petroleum products. ExxonMobil is a major manufacturer and marketer of commodity petrochemicals, including olefins, aromatics, polyethylene and polypropylene plastics and a wide variety of specialty products. ExxonMobil also has interests in electric power generation facilities. Affiliates of ExxonMobil conduct extensive research programs in support of these businesses.

The principal trading market for ExxonMobil’s common stock (NYSE: XOM) is the New York Stock Exchange.

The principal executive offices of ExxonMobil are located at 5959 Las Colinas Boulevard, Irving, TX 75039-2298, its telephone number is (972) 444-1000 and its website is www.exxonmobil.com .

XTO Energy Inc.

XTO Energy Inc., which is referred to in this proxy statement/prospectus as XTO Energy, a Delaware corporation, is engaged in the acquisition, development, exploitation and exploration of both producing oil and gas properties and unproved properties, and in the production, processing, marketing and transportation of oil and natural gas. XTO Energy’s proved reserves are principally located in relatively long-lived fields with an extensive base of hydrocarbons in place and, in most cases, well-established production histories concentrated in the Eastern Region, including the East Texas Basin, Haynesville Shale, northwestern Louisiana and Mississippi; the North Texas Region, including the Barnett Shale; the Mid-Continent and Rocky Mountain Region, including the Fayetteville, Woodford and Bakken Shales; the San Juan Region; the Permian Region; the South Texas and Gulf Coast Region, including the offshore Gulf of Mexico; and other regions, including Marcellus Shale and North Sea.

XTO Energy was incorporated in 1990 to acquire the business and properties of predecessor entities that were created from 1986 through 1989. XTO Energy’s initial public offering of common stock was completed in May 1993. XTO Energy was formerly known as Cross Timbers Oil Company and changed its name to XTO Energy Inc. in June 2001.

The principal trading market for XTO Energy’s common stock (NYSE: XTO) is the New York Stock Exchange.

The principal executive offices of XTO Energy are located at 810 Houston Street, Fort Worth, TX 76102, its telephone number is (817) 870-2800 and its website is www.xtoenergy.com .

ExxonMobil Investment Corporation

ExxonMobil Investment Corporation, which is referred to in this proxy statement/prospectus as Merger Sub, is a Delaware corporation and a wholly owned subsidiary of ExxonMobil. Merger Sub was formed solely for the purpose of consummating the merger. Merger Sub has not carried on any activities to date, except for activities incidental to its formation and activities undertaken in connection with the merger.

The principal executive offices of Merger Sub are located at 5959 Las Colinas Boulevard, Irving, TX 75039-2298 and its telephone number is (972) 444-1000.

The Merger (See Page 42).

ExxonMobil, Merger Sub and XTO Energy have entered into the Agreement and Plan of Merger, dated as of December 13, 2009, which, as it may be amended from time to time, is referred to in this proxy statement/prospectus as the merger agreement. Subject to the terms and conditions of the merger agreement and in accordance with Delaware law, Merger Sub will be merged with and into XTO Energy, with XTO Energy continuing as the surviving corporation. Upon completion of this transaction, which is referred to in this proxy statement/prospectus as the merger, XTO Energy will be a wholly owned subsidiary of ExxonMobil, and XTO Energy common stock will no longer be outstanding or publicly traded.

A copy of the merger agreement is attached as Annex A to this proxy statement/prospectus. You should read the merger agreement carefully because it is the legal document that governs the merger.

Special Meeting of XTO Energy Stockholders (See Page 38).

Meeting. The special meeting will be held in the Top of the Town Ballroom on the Twelfth Floor of The Fort Worth Club, 306 W. 7th Street, Fort Worth, Texas, on Friday, June 25, 2010 at 10:00 a.m., local time. At the special meeting, XTO Energy stockholders will be asked to vote on the following proposals:

Record Date . Only XTO Energy stockholders of record at the close of business on May 3, 2010 will be entitled to receive notice of and to vote at the special meeting. As of the close of business on the record date of May 3, 2010, there were 584,362,872 shares of XTO Energy common stock outstanding and entitled to vote at the meeting. Each holder of XTO Energy common stock is entitled to one vote for each share of common stock owned as of the record date.

Required Vote . To adopt the merger agreement, holders of a majority of the shares of XTO Energy common stock outstanding and entitled to vote on the proposal must vote in favor of adoption of the merger agreement. XTO Energy cannot complete the merger unless its stockholders adopt the merger agreement. Because approval is based on the affirmative vote of a majority of the outstanding shares of XTO Energy common stock, an XTO Energy stockholder’s failure to vote, an abstention from voting or the failure of an XTO Energy stockholder who holds his or her shares in “street name” through a broker or other nominee to give voting instructions to such broker or other nominee will have the same effect as a vote “AGAINST” adoption of the merger agreement .

To approve the adjournment of the special meeting, if necessary to solicit additional proxies if there are not sufficient votes to adopt the merger agreement at the time of the special meeting, the affirmative vote of holders of a majority of the shares of XTO Energy common stock present in person or represented by proxy at the special meeting and entitled to vote at the special meeting is required. Because approval of this proposal is based on the

affirmative vote of holders of a majority of the shares present in person or by proxy and entitled to vote, abstentions will have the same effect as a vote “ AGAINST ” such proposal, but failures to be present to vote and failures of XTO Energy stockholders who hold their shares in “street name” through brokers or other nominees to give voting instructions to such brokers or other nominees will have no effect on the vote held on such proposal.

Stock Ownership of and Voting by XTO Energy’s Directors and Executive Officers . At the close of business on the record date for the special meeting, XTO Energy’s directors and executive officers and their affiliates beneficially owned and had the right to vote 23,564,413 shares of XTO Energy common stock at the special meeting, which represents approximately 4% of the XTO Energy common stock entitled to vote at the special meeting. It is expected that XTO Energy’s directors and executive officers will vote their shares “ FOR ” the adoption of the merger agreement, although none of them has entered into any agreement requiring them to do so.

What XTO Energy Stockholders Will Receive in the Merger (See Page 86).

If the merger is completed, XTO Energy stockholders will be entitled to receive in the merger, for each share of XTO Energy common stock that they own, 0.7098 of a share of ExxonMobil common stock. The number of shares of ExxonMobil common stock delivered in respect of each share of XTO Energy common stock in the merger is referred to in this proxy statement/prospectus as the exchange ratio. ExxonMobil will not issue any fractional shares of its common stock in the merger. Instead, the total number of shares of ExxonMobil common stock that each XTO Energy stockholder will receive in the merger will be rounded down to the nearest whole number, and each XTO Energy stockholder will receive cash, without interest, for any fractional shares of ExxonMobil common stock that he or she would otherwise receive in the merger. The amount of cash for fractional shares will be calculated by multiplying the fraction of a share of ExxonMobil common stock that the XTO Energy stockholder would otherwise be entitled to receive in the merger by the closing sale price of a share of ExxonMobil common stock on the trading day immediately preceding the completion of the merger. The ExxonMobil common stock received based on the exchange ratio, together with any cash received in lieu of fractional shares, is referred to in this proxy statement/prospectus as the merger consideration.

Example: If you currently own 100 shares of XTO Energy common stock, you will be entitled to receive 70 shares of ExxonMobil common stock and cash for the market value of 0.98 shares of ExxonMobil common stock at the closing sale price of a share of ExxonMobil common stock on the trading day immediately preceding the completion of the merger.

The exchange ratio of 0.7098 of a share of ExxonMobil common stock is fixed, which means that it will not change between now and the date of the merger, regardless of whether the market price of either ExxonMobil or XTO Energy common stock changes. Therefore, the value of the merger consideration will depend on the market price of ExxonMobil common stock at the time XTO Energy stockholders receive ExxonMobil common stock in the merger. Based on the closing price of $72.83 for ExxonMobil common stock on the New York Stock Exchange on December 11, 2009, the last trading day before the public announcement of the merger agreement, the merger consideration represented approximately $51.69 in value for each share of XTO Energy common stock. Based on the closing price of $63.60 for ExxonMobil common stock on the New York Stock Exchange on May 14, 2010, the most recent practicable trading day prior to the date of this proxy statement/prospectus, the merger consideration represented approximately $45.14 in value for each share of XTO Energy common stock. The market price of ExxonMobil common stock will fluctuate prior to the merger, and the market price of ExxonMobil common stock when received by XTO Energy stockholders after the merger is completed could be greater or less than the current market price of ExxonMobil common stock.

Treatment of Equity Awards (See Page 87).

Upon completion of the merger, each option to purchase shares of XTO Energy common stock granted under XTO Energy’s equity compensation plans outstanding immediately prior to the completion of the merger will be converted into an option to acquire a number of shares of ExxonMobil common stock (rounded down to the nearest whole share) equal to the product of (a) the number of shares of XTO Energy common stock subject to the XTO Energy option immediately prior to the completion of the merger multiplied by (b) the exchange ratio in the merger. The exercise price per share of ExxonMobil common stock subject to a converted option will be an amount (rounded up to the nearest whole cent) equal to the quotient of (1) the exercise price per share of XTO Energy common stock subject to the XTO Energy option immediately prior to the completion of the merger divided by (2) the exchange ratio in the merger. Options with vesting conditions contingent on the achievement of specified XTO Energy stock targets will be adjusted based on the exchange ratio in the merger (rounded up to the nearest whole cent). Each converted option will remain subject to the same terms and conditions (including vesting terms) as were applicable to the XTO Energy option immediately prior to the completion of the merger, except for those converted options held by Bob R. Simpson, Keith A. Hutton, Vaughn O. Vennerberg, II, Louis G. Baldwin and Timothy L. Petrus. See “Interests of Certain Persons in the Merger—XTO Energy Named Executive Officers—Treatment of Stock Options and Other Equity-Based Awards” beginning on page 104 of this proxy statement/prospectus for a discussion of the terms and conditions applicable to converted options held by Messrs. Simpson, Hutton, Vennerberg, Baldwin and Petrus. Employees terminating employment at or within a stated period after the completion of the merger for reasons other than for cause or voluntary resignation without good reason (as defined in the applicable plans and arrangements) will have their option vesting accelerated upon such termination.

Upon completion of the merger, each restricted stock award or performance share award (which represents a share of XTO Energy common stock subject to vesting and forfeiture) granted under XTO Energy’s equity compensation plans outstanding immediately prior to the completion of the merger will be converted into a restricted stock award or performance share award, as applicable, relating to a number of shares of ExxonMobil common stock based on the exchange ratio in the merger (rounded down to the nearest whole share). Each converted restricted stock award or performance share award will remain subject to the same terms, restrictions and vesting schedules as were applicable to the XTO Energy restricted stock award or performance share award prior to the completion of the merger (with any vesting conditions contingent on the achievement of specified XTO Energy stock targets adjusted based on the exchange ratio in the merger, rounded up to the nearest whole cent), except for those performance share awards granted to Messrs. Simpson, Hutton, Vennerberg, Baldwin and Petrus prior to November 2009, performance share awards granted to certain employees (including the executive officers, other than Mr. Simpson) in November 2009 and performance share awards granted to Mr. Simpson in January 2010 pursuant to the terms of his existing employment agreement. Performance share awards granted to Messrs. Simpson, Hutton, Vennerberg, Baldwin and Petrus prior to November 2009 and to Mr. Simpson in January 2010 will become fully vested upon completion of the merger. Performance share awards granted to Messrs. Hutton, Vennerberg, Baldwin and Petrus in November 2009 will be converted into time-based restricted shares of ExxonMobil common stock, based on the exchange ratio. See “Interests of Certain Persons in the Merger—XTO Energy Named Executive Officers—Treatment of Stock Options and Other Equity-Based Awards” beginning on page 104 of this proxy statement/prospectus for a discussion of the terms, restrictions and vesting schedules applicable to converted performance share awards held by Messrs. Simpson, Hutton, Vennerberg, Baldwin and Petrus and “Interests of Certain Persons in the Merger—Other Executive Officers of XTO Energy—Treatment of Stock Options and Other Equity-Based Awards” beginning on page 109 of this proxy statement/prospectus for a discussion of the terms, restrictions and vesting schedules applicable to performance share awards held by other executive officers of XTO Energy. Employees terminating employment at or within a stated period after the completion of the merger for reasons other than for cause or voluntary resignation without good reason (as defined in the applicable plans and arrangements) will have vesting of their restricted stock and performance stock awards accelerated upon such termination.

Recommendation of the XTO Energy Board of Directors (See Page 55).

The XTO Energy board of directors (other than Jack P. Randall, who abstained from voting because he is a senior member of Jefferies & Company, Inc. (referred to in this proxy statement/prospectus as Jefferies), one of XTO Energy’s financial advisors) unanimously (i) determined that the merger agreement and the merger are advisable and in the best interests of XTO Energy and its stockholders, (ii) approved the merger and the merger agreement and (iii) resolved to recommend adoption of the merger agreement to the XTO Energy stockholders. The XTO Energy board of directors recommends that XTO Energy stockholders vote “FOR” adoption of the merger agreement.

For the factors considered by the XTO Energy board of directors in reaching its decision to approve the merger agreement, see “The Merger—XTO Energy Reasons for the Merger; Recommendation of the XTO Energy Board of Directors” beginning on page 55 of this proxy statement/prospectus.

In addition, the XTO Energy board of directors recommends that XTO Energy stockholders vote “ FOR ” the XTO Energy proposal to adjourn the special meeting, if necessary to solicit additional proxies if there are not sufficient votes to adopt the merger agreement at the time of the special meeting.

Opinion of XTO Energy’s Financial Advisor (See Page 60).

In connection with the merger, on December 13, 2009, Barclays Capital Inc., referred to in this proxy statement/prospectus as Barclays Capital, rendered its opinion to XTO Energy’s board of directors that, as of such date and based upon and subject to the qualifications, limitations and assumptions stated in its opinion, from a financial point of view, the exchange ratio in the proposed merger was fair to XTO Energy’s stockholders. The full text of Barclays Capital’s written opinion, which sets forth, among other things, the procedures followed, factors considered, assumptions made and qualifications and limitations of the review undertaken in rendering its opinion, is attached as Annex B to this proxy statement/prospectus. The opinion was delivered to the XTO Energy board of directors and addresses only the fairness, from a financial point of view, of the exchange ratio in the proposed merger. The opinion does not address any other aspect of the merger nor does it constitute a recommendation to any stockholder as to how such stockholder should vote or act with respect to any matters relating to the proposed merger or any other matter.

Ownership of ExxonMobil After the Merger (See Page 42).

Based on the number of shares of XTO Energy common stock (including XTO Energy restricted stock awards and performance share awards) and XTO Energy options outstanding as of May 14, 2010 and the number of shares of XTO Energy common stock to be issued immediately prior to completion of the merger pursuant to certain grant agreements with the named executive officers of XTO Energy, ExxonMobil expects to issue approximately 416,519,635 shares of its common stock to XTO Energy stockholders pursuant to the merger and reserve for issuance approximately 12,573,551 additional shares of ExxonMobil common stock in connection with the exercise or conversion of XTO Energy’s outstanding options. The actual number of shares of ExxonMobil common stock to be issued and reserved for issuance pursuant to the merger will be determined at the completion of the merger based on the exchange ratio of 0.7098 and the number of shares of XTO Energy common stock and XTO Energy options outstanding at such time. Immediately after completion of the merger, it is expected that former XTO Energy stockholders will own approximately 8% of the outstanding common stock of ExxonMobil common stock, based on the number of shares of XTO Energy and ExxonMobil common stock outstanding, on a fully diluted basis, as of May 14, 2010.

ExxonMobil Shareholder Approval Is Not Required.

ExxonMobil shareholders are not required to adopt the merger agreement or approve the merger or the issuance of the shares of ExxonMobil common stock in connection with the merger.

Interests of Certain Persons in the Merger (See Page 103).

In considering the recommendation of the XTO Energy board of directors with respect to the merger agreement, XTO Energy stockholders should be aware that the executive officers of XTO Energy and certain members of the XTO Energy board of directors have interests in the transactions contemplated by the merger agreement that are different from, or in addition to, the interests of XTO Energy stockholders generally. The XTO Energy board of directors was aware of these interests, and considered them, among other matters, in evaluating and negotiating the merger agreement and the merger, and in recommending that XTO Energy stockholders adopt the merger agreement.

In particular, each of the named executive officers of XTO Energy entered into a consulting agreement with XTO Energy and ExxonMobil that provides for, among other things, the payment of an annual consulting fee and completion bonus, a one-time grant of restricted ExxonMobil common stock or stock units and payment of severance and accelerated vesting of the restricted ExxonMobil common stock or stock units upon termination of the consulting relationship under certain circumstances. The estimated aggregate payments to be made to the named executive officers of XTO Energy pursuant to the consulting agreements are approximately $190,340,000, which represents a reduction from the approximately $304,690,000 in aggregate payments and benefits to which such executive officers otherwise would have been entitled under the existing agreements and plans if they continued to provide services through the completion of the merger and remained employed for one year following the merger. In addition, the named executive officers of XTO Energy held, in the aggregate, as of May 14, 2010, 470,000 unvested performance shares of XTO Energy common stock and unvested options to purchase 2,290,410 shares of XTO Energy common stock that will vest upon completion of the merger pursuant to the terms of the merger agreement.

Listing of ExxonMobil Stock and Delisting and Deregistration of XTO Energy Stock (See Page 78).

ExxonMobil will apply to have the shares of its common stock to be issued in the merger approved for listing on the New York Stock Exchange, where ExxonMobil common stock is currently traded. If the merger is completed, XTO Energy shares will no longer be listed on the New York Stock Exchange, and will be deregistered under the Securities Exchange Act of 1934, as amended, which is referred to in this proxy statement/prospectus as the Exchange Act.

No Appraisal Rights Available (See Page 75).

Under Delaware law, XTO Energy stockholders will not have appraisal rights in connection with the merger.

Completion of the Merger Is Subject to Certain Conditions (See Page 89).

The obligation of each of ExxonMobil, XTO Energy and Merger Sub to complete the merger is subject to the satisfaction (or, to the extent permitted by applicable law, waiver) of a number of conditions, including the following:

In addition, the obligations of ExxonMobil and Merger Sub to complete the merger are subject to the satisfaction (or, to the extent permitted by applicable law, waiver) of the following conditions:

ExxonMobil and XTO Energy cannot be certain when, or if, the conditions to the merger will be satisfied or waived, or that the merger will be completed.

The Merger May Not Be Completed Without All Required Regulatory Approvals (See Page 73).

Completion of the merger is conditioned upon the receipt of certain governmental clearances or approvals, including, but not limited to, the expiration or termination of the applicable waiting period relating to the merger under the HSR Act and the expiration or termination of the applicable waiting period, or receipt of approval, under the Dutch Competition Act.

ExxonMobil and XTO Energy have agreed to use their reasonable best efforts to obtain all regulatory approvals required to consummate the merger. However, in using their reasonable best efforts to obtain these required regulatory approvals, under the terms of the merger agreement, ExxonMobil is not required, and XTO Energy is not permitted without the consent of ExxonMobil, to take certain actions (such as divesting or holding separate assets or entering into settlements or consent decrees with governmental authorities) that would reasonably be expected to, individually or in the aggregate, restrict in any material respect, or otherwise negatively and materially impact, the natural gas (including natural gas liquids) exploration, production and sales businesses of either XTO Energy and its subsidiaries, taken as a whole, or ExxonMobil and its subsidiaries, taken as a whole.

ExxonMobil and XTO Energy each filed its required HSR notification and report form with respect to the merger on February 12, 2010, commencing the initial 30-day waiting period. This waiting period expired on March 15, 2010 without a request for additional information. ExxonMobil filed the required notification with respect to the merger under the Dutch Competition Act on February 11, 2010, and the Dutch Competition Authority approved the merger on March 9, 2010.

The Merger Is Expected to Occur in the Second Quarter of 2010 (See Page 85).

The merger will occur within two business days after the conditions to its completion have been satisfied or, to the extent permissible, waived, unless otherwise mutually agreed upon by the parties. As of the date of this proxy statement/prospectus, the merger is expected to occur in the second quarter of 2010. However, there can be no assurance as to when, or if, the merger will occur.

No Solicitation by XTO Energy (See Page 95).

Neither XTO Energy nor any of its subsidiaries will, nor will XTO Energy or any of its subsidiaries authorize or permit any of its or their officers, directors, employees or representatives to (i) solicit, initiate or otherwise knowingly facilitate or encourage the submission of any competing proposal from any third party relating to an acquisition of XTO Energy, (ii) enter into or participate in any discussions or negotiations regarding any such proposal or by furnishing any nonpublic information relating to XTO Energy or its subsidiaries to such third party, (iii) fail to make, withdraw or modify in a manner adverse to ExxonMobil the recommendation of the XTO Energy board of directors in favor of the adoption of the merger agreement, (iv) grant any waiver or release under any standstill or similar agreement, (v) approve any transaction, or any third party becoming an “interested stockholder,” under the Delaware anti-takeover statute or (vi) enter into an agreement relating to a competing acquisition proposal. Notwithstanding these restrictions, however, the merger agreement provides that, under specified circumstances at any time prior to the adoption of the merger agreement by XTO Energy stockholders:

The actions described in the preceding two bullets may be taken only if the XTO Energy board of directors determines in good faith, after consultation with its outside legal advisors, that failure to take such action would be inconsistent with its fiduciary duties under Delaware law. These restrictions in the merger agreement were the result of negotiations between XTO Energy and ExxonMobil, and the XTO Energy board of directors determined that these restrictions sought by ExxonMobil were reasonable and acceptable in light of the overall terms of the merger agreement, including the economic and other terms being offered by ExxonMobil, and the fact that these restrictions would not unduly impede the ability of a third party to make a superior bid to acquire XTO Energy if that third party were interested in doing so. See “The Merger—Background of the Merger” and “The Merger—XTO Energy Reasons for the Merger; Recommendation of the XTO Energy Board of Directors” beginning on pages 42 and 55, respectively, of this proxy statement/prospectus.

ExxonMobil has the right to terminate the merger agreement if, prior to the special meeting, the XTO Energy board of directors changes its recommendation in favor of the adoption of the merger agreement in a manner adverse to ExxonMobil. XTO Energy, however, does not have the right to terminate the merger agreement in connection with such a change of recommendation and, unless ExxonMobil terminates the merger agreement, XTO Energy would remain obligated to call and hold a special meeting of its stockholders for purposes of voting on a proposal to adopt the merger agreement.

Termination of the Merger Agreement (See Page 100).

The merger agreement may be terminated at any time before the completion of the merger by mutual written consent of ExxonMobil and XTO Energy.

The merger agreement may also be terminated prior to the completion of the merger by either ExxonMobil or XTO Energy if:

The merger agreement may also be terminated prior to the completion of the merger by ExxonMobil if:

Termination Fee Payable by XTO Energy (See Page 101).

XTO Energy has agreed to pay a fee of $900 million to ExxonMobil if the merger agreement is terminated under any of the following circumstances:

The XTO Energy board of directors, after consultation with XTO Energy’s legal and financial advisors, believed that, among other things, the termination fee payable by XTO Energy in such circumstances, as a percentage of the equity value of the transaction, was reasonable and would not unduly impede the ability of a third party to make a superior bid to acquire XTO Energy if such third party were interested in doing so, and was at a level consistent with, or favorable to, the fees payable in customary and comparable merger transactions. See “The Merger—XTO Energy Reasons for the Merger; Recommendation of the XTO Energy Board of Directors” beginning on page 55 of this proxy statement/prospectus.

Material U.S. Federal Income Tax Consequences of the Merger (See Page 75).

ExxonMobil and XTO Energy have structured the merger as a reorganization for U.S. federal income tax purposes. Accordingly, holders of shares of XTO Energy common stock will generally not recognize any gain or loss for U.S. federal income tax purposes on the exchange of their shares of XTO Energy common stock for ExxonMobil common stock in the merger, except for any gain or loss recognized in connection with any cash received in lieu of fractional ExxonMobil shares. It is a condition to the obligations of XTO Energy and ExxonMobil to complete the merger that each receive a legal opinion from its respective outside counsel that the merger will be a reorganization for U.S. federal income tax purposes.

Accounting Treatment (See Page 78).

In accordance with accounting principles generally accepted in the United States, ExxonMobil will account for the merger as an acquisition of a business.

Rights of XTO Energy Stockholders Will Change as a Result of the Merger (See Page 113).

XTO Energy stockholders will have different rights once they become ExxonMobil shareholders due to differences between the state corporate law applicable to, and the organizational documents of, ExxonMobil and XTO Energy. These differences are described in more detail under “Comparison of Shareholder Rights” beginning on page 113 of this proxy statement/prospectus.

Litigation Relating to the Merger (See Page 78).

Shortly following the announcement of the merger agreement, several putative stockholder class action complaints, and one non-class complaint, were filed against various combinations of XTO Energy, the members of the XTO Energy board of directors, ExxonMobil and Merger Sub in the District Court of Tarrant County, Texas, the Court of Chancery of the State of Delaware, and the United States District Court for the Northern District of Texas. These lawsuits challenge the proposed merger and generally allege, among other things, that the individual members of the XTO Energy board of directors have breached their fiduciary duties owed to the public stockholders of XTO Energy by approving the proposed merger and failing to take steps to maximize the value of XTO Energy to its public stockholders; that XTO Energy, ExxonMobil and Merger Sub aided and abetted such breaches of fiduciary duties; that the merger agreement improperly favors ExxonMobil and unduly restricts XTO Energy’s ability to negotiate with rival bidders; and that the preliminary proxy statement/prospectus filed with the United States Securities and Exchange Commission, which is referred to in this proxy statement/prospectus as the SEC, on February 1, 2010, and the amendments thereto, are materially misleading or omissive. These lawsuits generally seek, among other things, compensatory damages, declaratory and injunctive relief concerning the alleged fiduciary breaches and injunctive relief prohibiting the defendants from consummating the merger.

On April 21, 2010, the parties to the consolidated class action pending in the District Court of Tarrant County, Texas, as well as the parties to the actions filed in the Court of Chancery of the State of Delaware and the United States District Court for the Northern District of Texas, entered into a Stipulation and Agreement of Compromise, Settlement and Release to resolve all of these actions. On April 22, 2010, the District Court of Tarrant County, Texas entered an order preliminarily approving the proposed settlement and setting forth the schedule and procedures for notice to the stockholders of XTO Energy and the court’s final review of the settlement. The court scheduled a hearing for October 1, 2010 at 1:00 p.m. Central Time, at which the court will consider the fairness, reasonableness and adequacy of the settlement. See “The Merger—Litigation Relating to the Merger” beginning on page 78 of this proxy statement/prospectus for more information about the settlement of the stockholder litigation challenging the merger.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF EXXONMOBIL

The following table presents selected historical consolidated financial data of ExxonMobil. The data as of, and for the years ended, December 31, 2009, 2008, 2007, 2006 and 2005 are derived from ExxonMobil’s audited consolidated financial statements for those periods. The data as of, and for the three months ended, March 31, 2010 and 2009 are derived from ExxonMobil’s unaudited condensed consolidated financial statements for those periods. ExxonMobil’s management believes that the company’s interim unaudited financial statements have been prepared on a basis consistent with its audited financial statements and include all normal and recurring adjustments necessary for a fair presentation of the results for each interim period.

The information in the following table is only a summary and is not indicative of the results of future operations of ExxonMobil. You should read the following information together with ExxonMobil’s Annual Report on Form 10-K for the year ended December 31, 2009, ExxonMobil’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2010 and the other information that ExxonMobil has filed with the SEC and incorporated by reference into this proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 131 of this proxy statement/prospectus.

ExxonMobil is not required to furnish pro forma financial information with respect to the merger in this proxy statement/prospectus because XTO Energy would not be a significant subsidiary under any of the financial conditions specified in Rule 1-02(w) of SEC Regulation S-X, substituting 20% for 10% in each of those conditions in accordance with Rule 11.01(b)(1) of SEC Regulation S-X.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF XTO ENERGY

The following table presents selected historical consolidated financial data of XTO Energy. The data as of, and for the years ended, December 31, 2009, 2008, 2007, 2006 and 2005 are derived from XTO Energy’s audited consolidated financial statements for those periods. The data as of, and for the three months ended, March 31, 2010 and 2009 are derived from XTO Energy’s unaudited condensed consolidated financial statements for those periods. All per share data has been adjusted for the 5-for-4 stock split effected in December 2007 and the 4-for-3 stock split effected in March 2005. XTO Energy’s management believes that the company’s interim unaudited financial statements have been prepared on a basis consistent with its audited financial statements and include all normal and recurring adjustments necessary for a fair presentation of the results for each interim period.

The information in the following table is only a summary and is not indicative of the results of future operations of XTO Energy. You should read the following information together with XTO Energy’s Annual Report on Form 10-K for the year ended December 31, 2009, XTO Energy’s Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2010 and the other information that XTO Energy has filed with the SEC and incorporated by reference into this proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 131 of this proxy statement/prospectus.

SELECTED PROVED OIL AND GAS RESERVES OF XTO ENERGY

The following table presents selected estimated quantities of proved reserves of XTO Energy as of December 31, 2009, 2008 and 2007. The data as of December 31, 2009, 2008 and 2007 are derived from XTO Energy’s consolidated financial statements for those periods.

The information in the following table is only a summary and is not indicative of the results of future operations of XTO Energy. You should read the following information together with XTO Energy’s Annual Report on Form 10-K for the year ended December 31, 2009 and the other information that XTO Energy has filed with the SEC and incorporated by reference into this proxy statement/prospectus. See “Where You Can Find More Information” beginning on page 131 of this proxy statement/prospectus.

The process of estimating oil and gas reserves is complex and requires significant judgment as discussed in Item 1A, Risk Factors, in XTO Energy’s Annual Report on Form 10-K for the year ended December 31, 2009. As a result, XTO Energy has developed internal policies and controls for estimating and recording reserves. XTO Energy’s policies regarding booking reserves require proved reserves to be in compliance with the SEC definitions and guidance. XTO Energy’s policies assign responsibilities for compliance in reserves bookings to its reserves engineering group and require that reserve estimates be made by qualified reserves estimators, as defined by the Society of Petroleum Engineers’ standards. All qualified reserves estimators are required to receive education covering the fundamentals of SEC proved reserves assignments.

XTO Energy’s reserves engineering group is responsible for the internal review of reserve estimates and includes the Senior Vice President—Engineering. The Senior Vice President—Engineering has more than 20 years experience as a reserve engineer. The reserves engineering group is independent of any of XTO Energy’s operating areas. XTO Energy’s Chief Executive Officer is directly responsible for overseeing the reserves engineering group. No portion of the reserves engineering group’s compensation is directly dependent on the quantity of reserves booked.

The reserves engineering group reviews reserve estimates with XTO Energy’s third-party petroleum consultants, Miller and Lents, Ltd., an independent petroleum engineering firm. Miller and Lents’ primary technical person responsible for calculating XTO Energy’s reserves has more than 30 years of experience as a reserve engineer. Miller and Lents prepared the estimates of XTO Energy’s proved reserves as of December 31, 2009, 2008 and 2007. As prescribed by the SEC, such proved reserves were estimated using 12-month average oil and gas prices, based on the first-day-of-the-month price for each month in the period, and year end production and development costs for the December 31, 2009 estimate, without escalation. In previous years, such proved reserves were estimated using oil and gas prices and production and development costs as of December 31 of each such year, without escalation. None of XTO Energy’s natural gas liquid proved reserves are attributable to gas plant ownership.

COMPARATIVE PER SHARE DATA

The following table sets forth selected historical and unaudited pro forma combined per share information of ExxonMobil and XTO Energy.

Pro Forma Combined Per Share Information of ExxonMobil . The unaudited pro forma combined per share information of ExxonMobil below gives effect to the merger under the acquisition method of accounting, as if the merger had been effective on January 1, 2009, in the case of income from continuing operations and cash dividends data, and March 31, 2010, in the case of book value per share data, and assuming that 0.7098 of a share of ExxonMobil common stock had been issued in exchange for each outstanding share of XTO Energy common stock. The unaudited pro forma combined per share information of ExxonMobil is derived from the audited financial statements as of, and for the year ended, December 31, 2009 and the unaudited condensed consolidated financial statements as of, and for the three months ended, March 31, 2010 for ExxonMobil and XTO Energy.

The accounting for an acquisition of a business is based on the authoritative guidance for Business Combinations, which ExxonMobil adopted on January 1, 2009, and uses the fair value measurement concepts, which ExxonMobil adopted as required. Acquisition accounting requires, among other things, that most assets acquired and liabilities assumed be recognized at their fair values as of the acquisition date. Acquisition accounting is dependent upon certain valuations of XTO Energy’s assets and liabilities and other studies that have yet to commence or progress to a stage where there is sufficient information for a definitive measurement. Accordingly, the pro forma adjustments reflect the assets and liabilities of XTO Energy at their preliminary estimated fair values. Differences between these preliminary estimates and the final acquisition accounting will occur and these differences could have a material impact on the unaudited pro forma combined per share information set forth in the following table.

The unaudited pro forma combined per share information of ExxonMobil does not purport to represent the actual results of operations that ExxonMobil would have achieved had the companies been combined during these periods or to project the future results of operations that ExxonMobil may achieve after the merger.

Historical Per Share Information of ExxonMobil and XTO Energy . The historical per share information of each of ExxonMobil and XTO Energy below is derived from the audited financial statements as of, and for the year ended, December 31, 2009 and the unaudited condensed consolidated financial statements as of, and for the three months ended, March 31, 2010 for each such company.

Equivalent Pro Forma Combined Per Share Information of XTO Energy . The unaudited equivalent pro forma combined per share amounts of XTO Energy below are calculated by multiplying the unaudited pro forma combined per share amounts of ExxonMobil by the exchange ratio of 0.7098.

Generally . You should read the below information in conjunction with the selected historical financial information included elsewhere in this proxy statement/prospectus and the historical financial statements of ExxonMobil and XTO Energy and related notes that are incorporated into this proxy statement/prospectus by reference. See “Selected Historical Consolidated Financial Data of ExxonMobil”, “Selected Historical Consolidated Financial Data of XTO Energy” and “Where You Can Find More Information” beginning on pages 18, 19 and 131, respectively, of this proxy statement/prospectus.

COMPARATIVE PER SHARE MARKET PRICE AND DIVIDEND INFORMATION

Market Prices

The following table sets forth, for the periods indicated, the intra-day high and low sales prices per share for ExxonMobil and XTO Energy common stock as reported on the New York Stock Exchange, which is the principal trading market for both ExxonMobil and XTO Energy common stock, and the cash dividends declared per share of ExxonMobil and XTO Energy common stock (as adjusted, in the case of XTO Energy, for the 5-for-4 stock split effective on December 13, 2007).

The following table sets forth the closing sale price per share of ExxonMobil and XTO Energy common stock as reported on the New York Stock Exchange as of December 11, 2009, the last trading day before the public announcement of the merger agreement, and as of May 14, 2010, the most recent practicable trading day prior to the date of this proxy statement/prospectus. The table also shows the implied value of the merger consideration proposed for each share of XTO Energy common stock as of the same two dates. This implied value was calculated by multiplying the closing sale price of ExxonMobil common stock on the relevant date by the exchange ratio of 0.7098.

The market prices of ExxonMobil and XTO Energy common stock will fluctuate between the date of this proxy statement/prospectus and the completion of the merger. No assurance can be given concerning the market prices of ExxonMobil or XTO Energy common stock before the completion of the merger or ExxonMobil common stock after the completion of the merger. Because the exchange ratio is fixed in the merger agreement, the market value of the ExxonMobil common stock that XTO Energy stockholders will receive in connection with the merger may vary significantly from the prices shown in the table above. Accordingly, XTO Energy stockholders are advised to obtain current market quotations for ExxonMobil and XTO Energy common stock in deciding whether to vote for adoption of the merger agreement.

Dividends

ExxonMobil currently pays a quarterly dividend on its common stock and last paid a dividend on March 10, 2010 of $0.42 per share. On April 28, 2010, ExxonMobil declared a second-quarter dividend of $0.44 per share, payable on June 10, 2010 to holders of record on May 13, 2010.

XTO Energy currently pays a quarterly dividend on its common stock and last paid a dividend on April 15, 2010 of $0.125 per share. Under the terms of the merger agreement, during the period before the closing of the merger, XTO Energy is prohibited from declaring, setting aside or paying any dividend or other distribution except for its regular quarterly cash dividend, which is not to exceed $0.125 per share. On May 18, 2010, XTO Energy declared a second-quarter dividend of $0.125 per share, payable on June 15, 2010 to holders of record on May 28, 2010.

In addition, the merger agreement provides that ExxonMobil and XTO Energy will coordinate the declaration of dividends in respect of each company’s common stock before the completion of the merger so that the holders of ExxonMobil and XTO Energy common stock receive, in any quarter, one and only one dividend in respect of the shares of XTO Energy or ExxonMobil common stock held prior to the completion of the merger and those shares of ExxonMobil common stock issued in connection with the merger.

Any former XTO Energy stockholder who holds ExxonMobil common stock into which XTO Energy common stock has been converted in connection with the merger will receive whatever dividends are declared and paid on ExxonMobil common stock after the completion of the merger. However, no dividend or other distribution having a record date after the effective time of the merger will actually be paid with respect to any shares of ExxonMobil common stock exchangeable in connection with the merger until the certificates, if any, formerly representing shares of XTO Energy common stock have been surrendered, at which time any accrued dividends and other distributions on such shares of ExxonMobil common stock will be paid without interest. Any future dividends will be made at the discretion of the ExxonMobil board of directors. There can be no assurance that any future dividends will be declared or paid by ExxonMobil or as to the amount or timing of such dividends, if any.