Exhibit 5.1



                                                               January 11, 2001


U.S. Bancorp,
   U.S. Bank Place,
      601 Second Avenue South,
         Minneapolis, MN 55402

Ladies and Gentlemen:

            In connection with the registration under the Securities Act of 1933
(the "Act") of 1,002,000,000 shares (the "Securities") of Common Stock, par
value $0.01 per share, of U.S. Bancorp, a Delaware corporation (the "Company"),
to be issued in connection with the Agreement and Plan of Merger, dated as of
October 3, 2000, and amended as of October 23, 2000 and as of December 18, 2000
(the "Merger Agreement") by and between Firstar Corporation and the Company,
we, as your counsel, have examined such corporate records, certificates and
other documents, and such questions of law, as we have considered necessary
or appropriate for the purposes of this opinion. Upon the basis of such
examination, we advise you that, in our opinion, when the



U.S. Bancorp                                                                -2-


registration statement relating to the Securities (the "Registration Statement")
has become effective under the Act and the Securities to be issued under the
Merger Agreement have been duly issued and delivered as contemplated by the
Registration Statement and the Merger Agreement, the Securities will be
validly issued, fully paid and nonassessable.

            The foregoing opinion is limited to the Federal laws of the United
States and the Laws of the State of Delaware, and we are expressing no opinion
as to the effect of the laws of any other jurisdiction.

            We have relied as to certain matters on information obtained from
public officials, officers and counsel for the Company and other sources
believed by us to be responsible.

            We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to us under the heading "Validity of
U.S. Bancorp Common Stock" in the Proxy Statement/Prospectus included in the
Registration Statement. In giving such consent, we do not thereby admit that we
are in the category of persons whose consent is required under Section 7 of the
Act.

                                           Very truly yours,

                                           /s/ Sullivan & Cromwell