Exhibit 5.1

                        OPINION OF CLIFFORD CHANCE US LLP

July 24, 2003

Ligand Pharmaceuticals Incorporated
10275 Science Center Drive
San Diego, CA 92121

Re: Registration Statement on Form S-3

Ladies and Gentlemen:

We have acted as special counsel to Ligand Pharmaceuticals Incorporated, a
Delaware corporation (the "Company"), in connection with the Registration
Statement on Form S-3 (the "Registration Statement"), filed by the Company with
the Securities and Exchange Commission (the "Commission") under the Securities
Act of 1933, as amended (the "Securities Act"). The Registration Statement
covers offers and sales of up to 5,835,771 shares of the Company's common stock,
par value $0.001 per share (the "Shares"), that may be made from time to time by
the selling stockholders named in the Registration Statement.

This opinion is being furnished in accordance with the requirements of Item 16
of Form S-3 and Item 601(b)(5)(i) of Regulation S-K.

In rendering the opinion expressed below, we have examined and relied upon
originals or copies, certified or otherwise identified to our satisfaction, of
such corporate records, documents, certificates and other instruments as in our
judgment are necessary or appropriate. As to factual matters relevant to the
opinion set forth below, we have, with your permission, relied upon certificates
of officers of the Company and public officials. On the basis of the foregoing
and in reliance thereon, we are of the opinion that the Shares were duly
authorized, validly issued, fully paid and nonassessable when issued.

We consent to the filing of this opinion letter as Exhibit 5.1 to the
Registration Statement and to the reference to this firm under the caption
"Legal Matters" in the prospectus which is part of the Registration Statement.
In giving this consent, we do not thereby admit that we are within the category
of persons whose consent is required under Section 7 of the Securities Act, the
rules and regulations of the Commission promulgated thereunder, or Item 509 of
Regulation S-K.

This opinion letter is rendered as of the date first written above, and we
disclaim any obligation to advise you of facts, circumstances, events or
developments which hereafter may be brought to our attention and which may
alter, affect or modify the opinion expressed herein. Our opinion is expressly
limited to the matters set forth above and we render no opinion, whether by
implication or otherwise, as to any other matters relating to the Company or the
Shares.

                                Very truly yours,

                                /s/ Clifford Chance US LLP