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                                                                     EXHIBIT 5.1

                               FIFTH THIRD BANCORP
                               FIFTH THIRD CENTER
                             CINCINNATI, OHIO 45263

                                 January 8, 2001

Fifth Third Bancorp
38 Fountain Square Plaza
Cincinnati, Ohio 45263

      RE:   Issuance of 75,367 Shares of Common Stock of Fifth Third Bancorp
            Pursuant to Registration Statement on Form S-8 filed with the
            Securities and Exchange Commission

Gentlemen:

         I have acted as counsel to Fifth Third Bancorp, an Ohio corporation
("Company"), in connection with the issuance of 75,367 shares of the Company's
common stock, no par value ("Common Stock") pursuant to stock options of
Resource Management, Inc. ("Maxus") assumed by the Company in connection with
the Agreement and Plan of Merger ("Merger Agreement") dated as of October 2,
2000 by and among the Company, Maxus and certain shareholders of Maxus. On
January 2, 2001, Maxus merged into the Company and the Company assumed these
options.

         As counsel for the Company I have made such legal and factual
examinations and inquiries as I deem advisable for the purpose of rendering this
opinion. In addition, I have examined such documents and materials, including
the Articles of Incorporation, Code of Regulations, and other corporate records
of the Company, as I have deemed necessary for the purpose of this opinion.

         On the basis of the foregoing, I express the opinion that the 75,367
shares of Common Stock registered for issuance pursuant to the Registration
Statement are currently validly authorized and, when issued as contemplated by
the Registration Statement, will be legally issued, fully paid and nonassessable
shares of Common Stock of the Company.

         I hereby consent to the filing of this opinion as part of the
above-referenced Registration Statement and amendments thereto.

                                               Very truly yours,

                                               FIFTH THIRD BANCORP

                                               By   /s/ PAUL L. REYNOLDS
                                                    --------------------
                                                    Paul L. Reynolds, Counsel