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                                                                    EXHIBIT 5.01



                                                                     815,040-037



                      [Letterhead of O'Melveny & Myers LLP]



February 13, 2001



Southwest Gas Corporation
5241 Spring Mountain Road
P.O. Box 98510
Las Vegas, Nevada  89193

               RE:    $200,000,000 AGGREGATE PRINCIPAL AMOUNT OF 8.375% NOTES
                      DUE 2011

Ladies and Gentlemen:

        We have acted as special counsel in connection with the issuance and
sale by Southwest Gas Corporation (the "Company") of an aggregate of
$200,000,000 principal amount of the Company's 8.375% Notes due 2011 (the
"Notes") pursuant to that certain Underwriting Agreement dated as of February 7,
2001 and Pricing Agreement dated February 8, 2001 (the "Agreements") among the
Company, Goldman Sachs & Co., Banc of America Security LLC, Banc One Capital
Markets, Inc., BNY Capital Markets, Inc. and Merrill Lynch, Pierce, Fenner &
Smith Incorporated. The Notes are to be issued pursuant to an Indenture dated as
of July 15, 1996 (the "Original Indenture") between the Company and The Bank of
New York, as successor to Harris Trust and Savings Bank, as Trustee (the
"Trustee"), as supplemented and amended by the First Supplemental Indenture
dated as of August 1, 1996 (the "First Supplement"), the Second Supplemental
Indenture dated as of December 30, 1996 (the "Second Supplement") and the Third
Supplemental Indenture dated as of February 13, 2001 (the "Third Supplemental
Indenture", and together with the First Supplement, the Second Supplement and
the Original Indenture, the "Indenture").

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Southwest Gas Corporation, February 13, 2001 - Page 2



        On the basis of our consideration of such questions of law as we have
deemed relevant in the circumstances, we are of the opinion, subject to the
assumptions and limitations set forth herein, that the Notes have been duly
authorized by all necessary corporate action on the part of the Company and,
when each Note has been duly executed, authenticated and issued in accordance
with the provisions of the Indenture and upon payment for and delivery of the
Notes in accordance with the terms of the Agreements and the Indenture, will
constitute the legally valid and binding obligations of the Company, enforceable
against the Company in accordance with their terms, except as may be limited by
bankruptcy, insolvency, reorganization, moratorium or similar laws relating to
or affecting creditors' rights generally (including, without limitation,
fraudulent conveyance laws), and except that the enforceability of the Notes is
subject to the effect of general principles of equity, including, without
limitation, concepts of materiality, reasonableness, good faith and fair dealing
and the possible unavailability of specific performance or injunctive relief,
regardless of whether considered in a proceeding in equity or at law.

        We have, with your approval, assumed that the certificates for the Notes
will conform to the forms thereof examined by us, that the signatures on all
documents examined by us are genuine, that all items submitted as originals are
authentic, and that all items submitted as copies conform to the originals,
assumptions which we have not independently verified.

        We consent to the inclusion of this opinion in the Company's Current
Report on Form 8-K, event date February 8, 2001.


                                             Respectfully submitted


                                             /s/ O'Melveny & Myers LLP