EXHIBIT 5.1

[LETTERHEAD OF WILSON SONSINI GOODRICH & ROSATI]

February 11, 2003

The Gap, Inc.

Two Folsom Street

San Francisco, CA 94105

Re: Post-Effective Amendment No. 1 to Registration Statement No. 333-76523 on Form S-8

Ladies and Gentlemen:

At your request, we are rendering this opinion in connection with the proposed issuance of up to 22,500,000 shares of common stock, $0.05 par value (“Common Stock”), of The Gap, Inc., a Delaware corporation (the “Company”) under The Gap Inc. 1999 Stock Option Plan, as amended, and The Gap, Inc. 2002 Stock Option Plan, as amended (collectively, the “Plans”).

We have examined instruments, documents, and records which we deemed relevant and necessary for the basis of our opinion hereinafter expressed. In such examination, we have assumed the following: (a) the authenticity of original documents and the genuineness of all signatures; (b) the conformity to the originals of all documents submitted to us as copies; and (c) the truth, accuracy, and completeness of the information, representations, and warranties contained in the records, documents, instruments, and certificates we have reviewed.

Based on such examination, we are of the opinion that the 22,500,000 shares of Common Stock to be issued by the Company pursuant to the Plans are validly authorized shares of Common Stock and, when issued in accordance with the provisions of the Plans, will be legally issued, fully paid and non-assessable.

We hereby consent to the filing of this opinion as an exhibit to this Post-Effective Amendment No. 1 to Registration Statement No. 333-76523 on Form S-8 (the “Post-Effective Amendment”) and to the use of our name wherever it appears in the Post-Effective Amendment. In giving such consent, we do not consider that we are “experts” within the meaning of such term as used in the Securities Act of 1933, as amended, or the rules and regulations of the Securities and Exchange Commission issued thereunder with respect to any part of the Post-Effective Amendment, including this opinion, as an exhibit or otherwise.

Very truly yours,

/s/    WILSON SONSINI GOODRICH & ROSATI

WILSON SONSINI GOODRICH & ROSATI

Professional Corporation