Exhibit 5.1


                     [LETTERHEAD OF SULLIVAN & CROMWELL LLP]











                                                                  March 13, 2007


American International Group, Inc.
70 Pine Street,
New York, New York 10270

Ladies and Gentlemen:

     In connection with the several purchases today by the Underwriters named in
Schedule I to the Underwriting Agreement, dated March 6, 2007 (the "Underwriting
Agreement"), between American International Group, Inc., a Delaware corporation
(the "Company"), and Citigroup Global Markets Inc., Deutsche Bank Securities
Inc. and J.P. Morgan Securities Inc., as Representatives of the several
Underwriters named therein (the "Underwriters"), of $1,000,000,000 aggregate
principal amount of the Company's 6.25% Series A-1 Junior Subordinated
Debentures (the "Securities") issued pursuant to the Junior Subordinated Debt
Indenture, dated as of March 13, 2007, as supplemented by the First Supplemental
Indenture, dated as of March 13, 2007 (together, the "Indenture"), between the
Company and The Bank of New York,


                                                                             -2-

as Trustee (the "Trustee"), we, as counsel for the Company, 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, it is our opinion that:

                  (1) The Company has been duly incorporated and is an existing
         corporation in good standing under the laws of the State of Delaware.

                  (2) The Securities 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.


                                                                             -3-

     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 express no opinion as to the effect of the laws of any other
jurisdiction.

     We have relied as to certain matters upon information obtained from public
officials, officers of the Company and other sources believed by us to be
responsible, and we have assumed that the Indenture has been duly authorized,
executed and delivered by the Trustee, that the Securities conform to the
specimen thereof examined by us, that the Trustee's certificates of
authentication of the Securities have been manually signed by one of the
Trustee's authorized officers, and that the signatures on all documents examined
by us are genuine, assumptions which we have not independently verified.

     We hereby consent to the filing of this opinion as an exhibit to this
Current Report on Form 8-K. 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 Securities Act of 1933.



                                Very truly yours,



                               /s/ Sullivan & Cromwell LLP