UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES

EXCHANGE ACT OF 1934

(AMENDMENT NO.     )

Filed by the Registrant    x

Filed by a Party other than the Registrant    ¨

Check the appropriate box:

FIFTH THIRD BANCORP

(NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

(NAME OF PERSON(S) FILING PROXY STATEMENT, IF OTHER THAN THE REGISTRANT)

Payment of Filing Fee (Check the appropriate box):

38 FOUNTAIN SQUARE PLAZA

CINCINNATI, OHIO 45263

NOTICE OF ANNUAL MEETING OF SHAREHOLDERS

February 28, 2006

To the Shareholders of Fifth Third Bancorp:

You are cordially invited to attend the Annual Meeting of the Shareholders of Fifth Third Bancorp to be held at The Aronoff Center for the Arts, Jarson-Kaplan Theater, 650 Walnut Street, Cincinnati, Ohio on Tuesday, March 28, 2006 at 11:30 a.m. for the purposes of considering and acting upon the following:

Shareholders of record at the close of business on January 31, 2006 will be entitled to vote at the Annual Meeting.

All shareholders who find it convenient to do so are invited to attend the Annual Meeting in person. In any event, please sign and return the enclosed proxy card with this notice at your earliest convenience. If you hold shares of Fifth Third Bancorp common stock directly in your name, you may also vote over the internet or by telephone. If internet or telephone voting is available to you, voting instructions are printed on the proxy card sent to you.

If you plan to attend the Annual Meeting:

Please note that space limitations make it necessary to limit attendance only to shareholders of the Company and the holders of shareholder proxies. Admission to the Annual Meeting will be on a first-come, first-served basis and will require presentation of a valid driver’s license or other federal or state issued photo identification card. Shareholders of record should bring the admission ticket attached to their proxy card in order to be admitted to the meeting. “Street name” shareholders will need to bring a copy of a brokerage statement reflecting stock ownership as of the record date in order to be admitted to the meeting. Registration and seating will begin at approximately 11:00 a.m. Communication and recording devices will not be permitted at the Annual Meeting. A copy of the Regulations for Conduct at the Annual Meeting is attached as Annex 4 to the Proxy Statement.

By Order of the Board of Directors

Paul L. Reynolds

Secretary

FIFTH THIRD BANCORP

38 Fountain Square Plaza

Cincinnati, Ohio 45263

PROXY STATEMENT

The Board of Directors of Fifth Third Bancorp (the “Company”) is soliciting proxies, the form of which is enclosed, for the Annual Meeting of Shareholders to be held at The Aronoff Center for the Arts, Jarson-Kaplan Theater, 650 Walnut Street, Cincinnati, Ohio on Tuesday, March 28, 2006 at 11:30 a.m. (the “Annual Meeting”). Each of the 555,933,944 shares of Common Stock outstanding on January 31, 2006 is entitled to one vote on all matters acted upon at the Annual Meeting, and only shareholders of record on the books of the Company at the close of business on January 31, 2006 will be entitled to vote at the Annual Meeting, either in person or by proxy. The shares represented by all properly executed proxies which are sent to the Company will be voted as designated and each not designated will be voted and counted as described in this proxy statement. Each person giving a proxy may revoke it by giving notice to the Company in writing or in open meeting at any time before it is voted.

The laws of Ohio under which the Company is incorporated provide that if notice in writing is given by any shareholder to the President, a Vice President, or the Secretary of the Company not less than forty-eight (48) hours before the time fixed for holding a meeting of shareholders for the purpose of electing Directors that such shareholder desires that the voting at such election shall be cumulative, and if an announcement of the giving of such notice is made upon the convening of the meeting by the Chairman or Secretary or by or on behalf of the shareholder giving such notice, each shareholder shall have the right to cumulate such voting power as he or she possesses in voting for Directors.

The expense of soliciting proxies will be borne by the Company. Proxies will be solicited principally by mail, but may also be solicited by the Directors, officers, and other regular employees of the Company, who will receive no compensation therefor in addition to their regular compensation. Brokers and others who hold stock on behalf of others will be asked to send proxy material to the beneficial owners of the stock, and the Company will reimburse them for their expenses.

The Company has retained D.F. King & Co., Inc., a proxy solicitation firm, to assist the Company in soliciting proxies. The Company anticipates that the costs of D.F. King’s services will be approximately $9,000.

The Annual Report of the Company for the year 2005, including financial statements, has been delivered to all shareholders. Such report and financial statements are not a part of this Proxy Statement. This Proxy Statement and the form of proxy are first being sent to shareholders on or about February 28, 2006.

CERTAIN BENEFICIAL OWNERS

Under Section 13(d) of the Securities Exchange Act of 1934, a beneficial owner of a security is any person who directly or indirectly has or shares voting power or investment power over such security. Such beneficial owner under this definition need not enjoy the economic benefit of such securities. The following are the only shareholders known to the Company to be deemed to be beneficial owners of 5% or more of the Common Stock of the Company as of December 31, 2005:

ELECTION OF DIRECTORS

In accordance with the Company’s current Code of Regulations, the Board of Directors is classified into three classes. Each class is to be elected to separate three (3) year terms with each term expiring in different years. At each Annual Meeting the Directors or nominees constituting one class are elected for a three (3) year term. The term of those Directors listed below as Class II expires at the Annual Meeting on March 28, 2006 and this Class contains the nominees to be elected to serve until the Annual Meeting of Shareholders in 2009, unless the proposal to provide for the annual election of all Directors described in this Proxy Statement beginning on page 21 is approved in which case such Directors shall serve until the Annual Meeting of Shareholders in 2007. In accordance with the retirement guidelines set forth in the Company’s Corporate Governance Guidelines, Robert B. Morgan, a Class II Director, will retire at the Annual Meeting. Mr. Morgan has generously given valuable years of service to the Company. At its January 17, 2006 meeting the Board of Directors voted to decrease the size of the Board such that no vacancies will result from Mr. Morgan’s retirement. Any vacancies that occur after the Directors are elected may be filled by the Board of Directors in accordance with law for the remainder of the full term of the vacant directorship.

Director candidates are nominated by the Company’s Nominating and Corporate Governance Committee. The Nominating and Corporate Governance Committee’s Charter directs the Committee to investigate and assess the background and skills of potential candidates and to maintain an active file of suitable candidates for directors. The Nominating and Corporate Governance Committee is empowered to engage a third party search firm to assist, but the Committee currently believes that the existing directors and executive management of the Company and its subsidiaries have significant networks of business contacts that likely will form the pipeline from which candidates will be identified. Upon identifying a candidate for serious consideration, one or more members of the Nominating and Corporate Governance Committee would initially interview such candidate. If a candidate merited further consideration, the candidate would subsequently interview with all other Committee members (individually or as a group), meet the Company’s Chief Executive Officer and other Executive Officers and ultimately meet many of the other Directors. The Nominating and Corporate Governance Committee would elicit feedback from all persons who met the candidate and then determine whether or not to nominate the candidate.

The Company’s Corporate Governance Guidelines set forth the following criteria for Directors: independence; highest personal and professional ethics and integrity; willing to devote sufficient time to fulfilling

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duties as a Director; impact on the diversity of the Board’s overall experience in business, government, education, technology and other areas relevant to the Company’s business; impact on the diversity of the Board’s composition in terms of age, skills, ethnicity and other factors relevant to the Company’s business; and number of other public company boards on which the candidate may serve (generally, should not be more than three public company boards in addition to the Company). The Company’s Corporate Governance Guidelines provide that shareholders may propose nominees by submitting the names and qualifications of such persons to the Nominating and Corporate Governance Committee no later than December 31 of each year. Submissions are to be addressed to the Nominating and Corporate Governance Committee at the Company’s executive offices, which submissions will then be forwarded to the Committee. The Nominating and Corporate Governance Committee would then evaluate the possible nominee using the criteria outlined above and would consider such person in comparison to all other candidates. The Nominating and Corporate Governance Committee is not obligated to nominate any such individual for election. No such shareholder nominations have been received by the Company for this Annual Meeting. Accordingly, no rejections or refusals of such candidates have been made by the Company.

The Nominating and Corporate Governance Committee did not hire any director search firm in 2005 or 2006 and, accordingly, paid no fees to any such company. As indicated above, however, the Nominating and Corporate Governance Committee may do so in the future if necessary.

The Nominating and Corporate Governance Committee of the Board of Directors has nominated for election as Class II Directors the following four (4) persons, all of whom are presently serving as Class II Directors of the Company: John F. Barrett, George A. Schaefer, Jr., John J. Schiff, Jr. and Dudley S. Taft. Unless instructed otherwise, it is the intention of the persons named in the Proxy to vote for the election of all nominees named. If any nominee(s) shall be unable to serve, which is not now contemplated, the proxies will be voted for such substitute nominee(s) as the Nominating and Corporate Governance Committee of the Board of Directors recommends. Proxies in the form solicited hereby which are returned to the Company will be voted in favor of the four (4) nominees specified above unless otherwise instructed by the shareholder. Shares not voted by brokers and other entities holding shares on behalf of beneficial owners will not be counted and will have no effect on the outcome of the election. Nominees receiving the four (4) highest totals of votes cast in the election will be elected as directors.

Neither the Board nor the Nominating and Corporate Governance Committee has implemented a formal policy regarding director attendance at the Annual Meeting. Typically, the Board holds its annual organizational meeting directly following the Annual Meeting, which results in most directors being able to attend the Annual Meeting. In 2005, all 15 Directors attended the Annual Meeting.

The following tables set forth information with respect to each Class II Director, including the retiring Director and the nominees for re-election at the Annual Meeting, and with respect to the continuing incumbent Directors in Classes I and III of the Board of Directors. The Board of Directors has determined that all Directors have met the independence standards of Rule 4200(a)(15) of the National Association of Securities Dealers listing standards with the exceptions of Messrs. Schaefer and Schiff.

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BOARD OF DIRECTORS, ITS COMMITTEES, MEETINGS AND FUNCTIONS

The Board of Directors of the Company met five (5) times during 2005. The Company’s Board of Directors also regularly holds executive sessions of those members of the Board of Directors who meet the then current standards of independence. The chairman at these executive sessions is the Chairman of the Nominating and Corporate Governance Committee, who serves as the lead director of the Board in performing such other jobs as the independent Directors may determine.

There are six (6) committees of the Board of Directors: Executive, Audit, Compensation, Nominating and Corporate Governance, Risk and Compliance, and Trust.

The Executive Committee of the Company serves in a dual capacity as the Executive Committee of the Company and Fifth Third Bank, an Ohio banking corporation (the “Bank”). Under Ohio law, the Executive Committee has the power to act between meetings of the Board on virtually all matters that the Board could act upon. The Board of Directors has adopted an Executive Committee Charter which may be found in the Corporate Governance Section of the Company’s website at www.53.com. The Executive Committee met twelve (12) times in 2005 and consisted of Messrs. Hill, Koch, Schaefer, Schiff and Taft.

The Audit Committee of the Company serves in a dual capacity as the Audit Committee of the Company and the Bank. Thirteen (13) meetings of this Committee were held during 2005. This Committee’s functions include the engagement of the independent registered public accounting firm, reviewing with that firm the plans and results of the audit engagement of the Company, approving the annual audit plan and reviewing the results of the procedures for internal auditing, reviewing the independence of the independent registered public accounting firm, reviewing the Company’s financial results and Securities and Exchange Commission filings, reviewing the design and effectiveness of the Company’s internal controls and similar functions and approving all auditing and non-auditing services performed by its independent registered public accounting firm. Another function of this Committee is to carry out the statutory requirements of a bank audit committee as prescribed under applicable law. The Board of Directors has adopted a written charter for the Audit Committee, which may be found in the Corporate Governance Section of the Company’s website at www.53.com. The Audit Committee members for 2005 were Messrs. Allen, Barrett, Hackett, Morgan and Ms. Herschede. All members of the Audit Committee met the independence standards of Rule 4200(a)(15) and the audit committee qualifications of Rule 4350(d)(2) of the National Association of Securities Dealers listing standards. The Board of Directors has determined that Darryl F. Allen is an audit committee financial expert for the Company and is independent as described in the preceding sentence. The formal report of the Audit Committee with respect to the year 2005 begins on page 17 herein.

The Company has a Compensation Committee comprised entirely of independent Directors. Executive compensation and equity plan allocations are determined by this Committee of the Board of Directors. The Board of Directors has adopted a Compensation Committee Charter which may be found in the Corporate Governance Section of the Company’s website at www.53.com. This Committee consisted of Messrs. Hill, Lowe, and Rogers, and met five (5) times during 2005. The formal report of the Compensation Committee with respect to 2005 compensation begins on page 13 herein.

The Company has a Nominating and Corporate Governance Committee comprised entirely of independent Directors. This Committee develops and recommends to the Board corporate governance policies and guidelines for the Company and for the identification and nomination of Director and committee member candidates and nominates Directors for election to the Board and appointment to committee membership. The Board of Directors has adopted a Nominating and Corporate Governance Committee Charter which may be found in the Corporate Governance Section of the Company’s website at www.53.com. This Committee consisted of Messrs. Allen, Koch, Rogers and Taft and met three (3) times during 2005.

The Company’s Risk and Compliance Committee serves in a dual capacity as the Risk and Compliance Committee of the Company and the Bank. The Committee oversees management’s compliance with all of the

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Company’s regulatory obligations arising under applicable federal and state banking laws, rules and regulations, including any terms and conditions required from time to time by any action, formal or informal, of any federal or state banking regulatory agency or authority and any responses of management to any inquiries from any applicable banking regulator, and oversees management’s implementation and enforcement of the Company’s risk management policies and procedures. The Board of Directors has adopted a Risk and Compliance Committee Charter which may be found in the Corporate Governance Section of the Company’s website at www.53.com. This Committee met four (4) times in 2005 and consisted of Messrs. Barrett, Meijer and Traylor.

The Company has a Trust Committee which serves in a dual capacity as the Trust Committee of the Company and the Bank. The Committee reviews the fiduciary activities of the Bank and, more generally, oversees the structure for fiduciary activities for each of the Company’s subsidiary banks, including the Bank. In this regard, the Committee has responsibility to report risks identified in its review of such fiduciary activities to the Company’s Risk and Compliance Committee. The Committee also has overall responsibility for evaluating and approving the fiduciary policies of the Company and its bank subsidiaries. The Board of Directors has adopted a Trust Committee Charter which may be found in the Corporate Governance Section of the Company’s website at www.53.com. This Committee consisted of Messrs. Livingston, Lowe, Schaefer and Ms. Herschede, and met four (4) times during 2005.

No member of the Board of Directors of the Company attended less than 75% of the aggregate meetings of the Board of Directors and all committees on which such Director served during 2005.

The Board of Directors has adopted the Fifth Third Bancorp Corporate Governance Guidelines which may be found in the Corporate Governance Section of the Company’s website at www.53.com. The Board of Directors has also adopted the Fifth Third Bancorp Code of Business Conduct and Ethics which may also be found in the Corporate Governance Section of the Company’s website at www.53.com.

The Audit Committee has established Fifth Third’s EthicsLine, a toll free hotline through which confidential complaints may be made by employees regarding: illegal or fraudulent activity; questionable accounting, internal controls or auditing matters; conflicts of interest, dishonest or unethical conduct; disclosures in the Company’s SEC reports, bank regulatory filings and other public disclosures that are not full, fair, accurate, timely and understandable; violations of the Company’s Code of Business Conduct and Ethics; and/or any other violations of laws, rules or regulations. Complaints submitted through this process are presented to the Audit Committee on a regular, periodic basis.

Shareholders may communicate directly to the Board of Directors in writing by sending a letter to the Board at: Fifth Third Bancorp Board of Directors, 38 Fountain Square Plaza, MD 10AT76, Cincinnati OH, 45263 or by a secure e-mail via the Company’s website at www.53.com. All communications directed to the Board of Directors will be received and processed by the Fifth Third Legal Department and will be transmitted to the Chairman of the Nominating and Corporate Governance Committee (who serves as the lead director of the Board of Directors) without any editing or screening by the Legal Department.

EXECUTIVE COMPENSATION

Set forth below are tables showing for the Chief Executive Officer and the four other highest-paid Executive Officers of the Company: (1) in summary form, the compensation paid for the last three years; (2) the SARs granted and options exercised; (3) the restricted stock granted, (4) the performance units granted, and (5) beneficial ownership of the Company’s Common Stock.

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Summary

The following table is a summary of certain information concerning the compensation awarded, paid to, or earned by the Company’s Chief Executive Officer and each of the Company’s other highly compensated Executive Officers (the “named executives”) during each of the last three fiscal years or such shorter period during which such individuals served as an Executive Officer of the Company.

SUMMARY COMPENSATION TABLE

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Stock Appreciation Rights/Stock Options

The following table sets forth information concerning individual grants of stock appreciation rights (“SARs”) to purchase the Company’s Common Stock made to the named executives in 2005:

SAR GRANTS IN LAST FISCAL YEAR

The Company made no grants of stock options to purchase the Company’s Common Stock to the named executives in 2005.

The following table sets forth certain information regarding individual exercises of stock options during 2005 by each of the named executives.

AGGREGATED OPTION/SAR EXERCISES IN LAST FISCAL YEAR

The named executives did not exercise any SARs in 2005.

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Performance Units

The following table sets forth information concerning individual grants of performance units (a share denominated award under the Company’s Incentive Compensation Plan) made to the named executives in 2005:

LONG TERM INCENTIVE PLAN—AWARDS OF PERFORMANCE UNITS IN LAST FISCAL YEAR