1
                                                                     EXHIBIT 5.1






                       [THE WILLIAMS COMPANIES LETTERHEAD]






August 1, 2001



The Williams Companies, Inc.
One Williams Center
Tulsa, OK  74172

Ladies and Gentlemen:

The Williams Companies, Inc., a Delaware corporation ("Williams"), contemplates
filing a Registration Statement on Form S-8 under the Securities Act of 1933, as
amended (the "Registration Statement"), relating to the registration of Common
Stock of Williams, $1.00 par value (the "Common Stock"), and associated
Preferred Stock Purchase Rights (the "Rights"), to be issued pursuant to the
terms of The Williams Companies, Inc. 2001 Stock Plan (the "Plan").

As counsel for Williams, I have examined originals or copies, certified or
otherwise identified to my satisfaction, of such documents, corporate records,
certificates of public officials and other instruments and legal matters as I
deem relevant to the authorization and issuance of the Common Stock and the
Rights under the terms of the Plan. Based on such examination, it is my opinion
that the Common Stock has been duly authorized and, when issued and delivered in
accordance with the terms of the Plan, will be validly issued, fully paid and
nonassessable, and the Rights to which holders of Common Stock issued under the
Plan will be entitled, have been duly authorized and when issued in accordance
with their terms, will be validly issued.

I hereby consent to the filing of this opinion with the Securities and Exchange
Commission as Exhibit 5.1 to the Registration Statement.

Best regards,

/s/ Suzanne H. Costin


Suzanne H. Costin