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                                                                     Exhibit 5.1



                      [Letterhead of Sullivan & Cromwell]



                                                           May 3, 2000




The Goldman Sachs Group, Inc.,
   85 Broad Street,
      New York, New York 10004.

Ladies and Gentlemen:

         In connection with the registration under the Securities Act of 1933
(the "Act") by The Goldman Sachs Group, Inc., a Delaware corporation (the
"Company"), of $25,000,000,000 aggregate amount of its senior and subordinated
debt securities, warrants, purchase contracts, units comprised of the foregoing,
preferred stock and depositary shares representing preferred stock
(collectively, the "Securities"), we, as your counsel, have examined such
corporate records, certificates and other documents, including the resolutions
of the Company's board of directors authorizing the issuance of the Securities
(the "Resolutions"), and such questions of law, as we have
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The Goldman Sachs Group, Inc.                                              -2-


considered necessary or appropriate for the purposes of this opinion.

         Upon the basis of such examination, we advise you that, in our opinion:

                  (1) Debt Securities. The indenture relating to the senior debt
         securities, which is dated as of May 19, 1999, has been duly
         authorized, executed and delivered by the Company, and the indenture
         relating to the subordinated debt securities, in the form filed as an
         exhibit to the Registration Statement, has been duly authorized by the
         Company. When the Registration Statement has become effective under the
         Act, when the indenture relating to the subordinated debt securities
         has been duly executed and delivered substantially in the form so
         filed, when the terms of the debt securities and of their issuance and
         sale have been duly established in conformity with the applicable
         indentures so as not to violate any applicable law or result in a
         default under or breach of any agreement or instrument binding upon the
         Company, and so as to comply with any requirement or restriction
         imposed by any court or governmental body having jurisdiction over the
         Company, and when the debt securities have been duly executed and
         authenticated in accordance with the
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The Goldman Sachs Group, Inc.                                              -3-


         applicable indentures and issued and sold as contemplated in the
         Registration Statement, and if all the foregoing actions are taken
         pursuant to the authority granted in the Resolutions, the debt
         securities will constitute valid and legally binding obligations of the
         Company, subject to bankruptcy, insolvency, fraudulent transfer,
         reorganization, moratorium and similar laws of general applicability
         relating to or affecting creditors' rights and to general equity
         principles. The debt securities covered by the opinion in this
         paragraph include any debt securities that may be issued as part of the
         units or upon exercise or otherwise pursuant to the terms of any other
         Securities, as well as any purchase contracts that may be issued under
         the indentures relating to the debt securities.

                  (2) Warrants. When the Registration Statement has become
         effective under the Act, when the terms of the warrant agreements under
         which the warrants are to be issued have been duly established and the
         warrant agreements have been duly executed and delivered, when the
         terms of the warrants and of their issuance and
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The Goldman Sachs Group, Inc.                                              -4-


         sale have been duly established in conformity with the applicable
         warrant agreements and when the warrants have been duly executed and
         authenticated in accordance with the applicable warrant agreements and
         issued and sold as contemplated in the Registration Statement, and if
         all the foregoing actions are taken pursuant to the authority granted
         in the Resolutions and so as not to violate any applicable law or
         result in a default under or breach of any agreement or instrument
         binding upon the Company, and so as to comply with any requirement or
         restriction imposed by any court or governmental body having
         jurisdiction over the Company, the warrants will constitute valid and
         legally binding obligations of the Company, subject to bankruptcy,
         insolvency, fraudulent transfer, reorganization, moratorium and similar
         laws of general applicability relating to or affecting creditors'
         rights and to general equity principles. The warrants covered by the
         opinion in this paragraph include any warrants that may be issued as
         part of the units or upon exercise or otherwise pursuant to the terms
         of any other Securities.
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The Goldman Sachs Group, Inc.                                              -5-


                  (3) Purchase Contracts. When the Registration Statement has
         become effective under the Act, when the terms of the governing
         instruments or agreements under which the purchase contracts are to be
         issued have been duly established and the governing documents have been
         duly executed and delivered, when the terms of the purchase contracts
         and of their issuance and sale have been duly established in conformity
         with the applicable governing documents and when the purchase contracts
         have been duly executed and authenticated in accordance with the
         applicable governing documents and issued and sold as contemplated in
         the Registration Statement, and if all the foregoing actions are taken
         pursuant to the authority granted in the Resolutions and so as not to
         violate any applicable law or result in a default under or breach of
         any agreement or instrument binding upon the Company, and so as to
         comply with any requirement or restriction imposed by any court or
         governmental body having jurisdiction over the Company, the purchase
         contracts will constitute valid and legally binding obligations of the
         Company, subject to bankruptcy, insolvency, fraudulent transfer,
         reorganization,
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The Goldman Sachs Group, Inc.                                              -6-


         moratorium and similar laws of general applicability relating to or
         affecting creditors' rights and to general equity principles. The
         purchase contracts covered by the opinion in this paragraph include any
         purchase contracts that may be issued as part of the units or upon
         exercise or otherwise pursuant to the terms of any other Securities,
         but they do not include any purchase contracts to be issued under the
         indentures relating to the debt securities.

                  (4) Units. When the Registration Statement has become
         effective under the Act, when the terms of the unit agreements under
         which the units are to be issued have been duly established and the
         unit agreements have been duly executed and delivered, when the terms
         of the units and of their issuance and sale have been duly established
         in conformity with the applicable unit agreements and when the units
         have been duly executed and authenticated in accordance with the
         applicable unit agreements and issued and sold as contemplated in the
         Registration Statement, and if all the foregoing actions are taken
         pursuant to the authority granted in the Resolutions and so as not to
         violate any applicable
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The Goldman Sachs Group, Inc.                                              -7-


         law or result in a default under or breach of any agreement or
         instrument binding upon the Company, and so as to comply with any
         requirement or restriction imposed by any court or governmental body
         having jurisdiction over the Company, the units will constitute valid
         and legally binding obligations of the Company, subject to bankruptcy,
         insolvency, fraudulent transfer, reorganization, moratorium and similar
         laws of general applicability relating to or affecting creditors'
         rights and to general equity principles. The units covered by the
         opinion in this paragraph include any units that may be issued upon
         exercise or otherwise pursuant to the terms of any other Securities.

                  (5) Preferred Stock. When the Registration Statement has
         become effective under the Act, when the terms of the preferred stock
         and of its issuance and sale have been duly established in conformity
         with the Company's certificate of incorporation so as not to violate
         any applicable law or result in a default under or breach of any
         agreement or instrument binding upon the Company, and so as to comply
         with any requirement
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The Goldman Sachs Group, Inc.                                              -8-


         or restriction imposed by any court or governmental body having
         jurisdiction over the Company, when an appropriate certificate of
         designations with respect to the preferred stock has been duly filed
         with the Secretary of State of the State of Delaware and when the
         preferred stock has been duly issued and sold as contemplated by the
         Registration Statement, and if all the foregoing actions are taken
         pursuant to the authority granted in the Resolutions, the preferred
         stock will be validly issued, fully paid and non-assessable. The
         preferred stock covered in the opinion in this paragraph includes any
         preferred stock that may be represented by depositary shares or may be
         issued upon exercise or otherwise pursuant to the terms of any other
         Securities.

                  (6) Depositary Shares. When the Registration Statement has
         become effective under the Act, when the terms of the deposit agreement
         under which the depositary shares are to be issued have been duly
         established and the deposit agreement has been duly executed and
         delivered, when the terms of the
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The Goldman Sachs Group, Inc.                                              -9-


         depositary shares and of their issuance and sale have been duly
         established in conformity with the deposit agreement, when the
         preferred stock represented by the depositary shares has been duly
         delivered to the depositary and when the depositary receipts evidencing
         the depositary shares have been duly issued against deposit of the
         preferred stock in accordance with the deposit agreement and issued and
         sold as contemplated by the Registration Statement, and if all the
         foregoing actions are taken pursuant to the authority granted in the
         Resolutions and so as not to violate any applicable law or result in a
         default under or breach of any agreement or instrument binding upon the
         Company, and so as to comply with any requirement or restriction
         imposed by any court or governmental body having jurisdiction over the
         Company, the depositary receipts evidencing the depositary shares will
         be validly issued and will entitle the holders thereof to the rights
         specified in the depositary shares and the deposit agreement, subject
         to bankruptcy, insolvency, fraudulent transfer, reorganization,
         moratorium and similar laws of general applicability relating to or
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The Goldman Sachs Group, Inc.                                             -10-


         affecting creditors' rights and to general equity principles. The
         depositary shares covered by the opinion in this paragraph include any
         depositary shares that may be issued upon exercise of or otherwise
         pursuant to any other Securities.

         We note that, as of the date of this opinion, a judgment for money in
an action based on a Security denominated in a foreign currency or currency unit
in a Federal or state court in the United States ordinarily would be enforced in
the United States only in United States dollars. The date used to determine the
rate of conversion of the foreign currency or currency unit in which a
particular Security is denominated into United States dollars will depend upon
various factors, including which court renders the judgment. In the case of a
Security denominated in a foreign currency, a state court in the State of New
York rendering a judgment on such Security would be required under Section 27 of
the New York Judiciary Law to render such judgment in the foreign currency in
which the Security is denominated, and such judgment would be converted into
United States dollars at the exchange rate prevailing on the date of entry of
the judgment.
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The Goldman Sachs Group, Inc.                                             -11-


        The foregoing opinion is limited to the Federal laws of the United
States, the laws of the State of New York and the General Corporation Law 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 of the Company and other sources believed by us to be
responsible. We have assumed, without independent verification, that the
indenture relating to the senior debt securities has been duly authorized,
executed and delivered by the trustee thereunder, that all other governing
documents under which the Securities are to be issued, as well as the purchase
contracts, if applicable, will have been duly authorized, executed and delivered
by all parties thereto other than the Company and that the signatures on
documents examined by us are genuine. We have further assumed that the issuance
or delivery by the Company of any securities other than the Securities, or of
any other property, upon exercise or otherwise pursuant to the terms of the
Securities will be effected pursuant to the authority granted in the Resolutions
and so as not to violate any applicable law or result in a default under or
breach of any agreement or
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The Goldman Sachs Group, Inc.                                             -12-

instrument binding on the Company, and so as to comply with any requirement or
restriction imposed by any court or governmental body having jurisdiction over
the Company. Finally, we have assumed that the authority granted in the
Resolutions will remain in effect at all relevant times.

        We are expressing no opinion as to any obligations that parties other
than the Company may have under or in respect of the Securities or as to the
effect that their performance of such obligations may have upon any of the
matters referred to above.

        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
the Securities" in the Prospectus. 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