EXHIBIT 5.1


                 [LETTERHEAD OF WACHTELL, LIPTON, ROSEN & KATZ]


                                 August 11, 2006


Cathay General Bancorp
777 N. Broadway
Los Angeles, CA 90012

RE: REGISTRATION STATEMENT ON FORM S-4, AS AMENDED (333-135976)

Ladies and Gentlemen:

          We have acted as special counsel to Cathay General Bancorp, a Delaware
corporation (the "COMPANY"), in connection with the preparation and filing of
the Registration Statement on Form S-4 of the Company (as amended, the
"REGISTRATION STATEMENT,") relating to shares of common stock, par value $0.01
per share (the "COMMON STOCK"), of the Company to be issued by the Company in
connection with the merger of New Asia Bancorp, Inc., a Delaware corporation,
with and into the Company.

          In rendering this opinion, we have examined such corporate records and
other documents, and we have reviewed such matters of law, as we have deemed
necessary or appropriate. In rendering this opinion, we have, with your consent,
relied upon oral and written representations of officers of the Company and
certificates of officers of the Company and public officials with respect to the
accuracy of the factual matters addressed in such representations and
certificates. In addition, in rendering this opinion we have, with your consent,
assumed the genuineness of all signatures or instruments relied upon by us, and
the conformity of certified copies submitted to us with the original documents
to which such certified copies relate.

          We are members of the Bar of the State of New York and we express no
opinion as to the laws of any jurisdiction other than the federal laws of the
United States, the General Corporation Law of the State of Delaware and the laws
of the State of New York.






          Based on and subject to the foregoing, we are of the opinion that the
Common Stock is or will be, upon issuance, legally authorized and, when the
Registration Statement has been declared effective by order of the Securities
and Exchange Commission and the Common Stock has been issued and paid for upon
the terms and conditions set forth in the Registration Statement, the Common
Stock will be validly issued, fully paid and nonassessable.

          We hereby consent to be named in the Registration Statement and in the
related prospectus contained therein as the attorneys who passed upon the
legality of the Common Stock and to the filing of a copy of this opinion as
Exhibit 5.1 to the Registration Statement. 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, as amended.

                                  Very truly yours,

                                  /s/ Wachtell, Lipton, Rosen & Katz