Exhibit 5.1

August 8, 2007

Nektar Therapeutics

201 Industrial Road

San Carlos, CA 94070

Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection with the filing by Nektar Therapeutics (the “Company”) of a Registration Statement on Form S-8 (the “Registration Statement”) with the Securities and Exchange Commission covering the offering of up to 300,000 shares of the Company’s Common Stock, $0.0001 par value, (the “Shares”) pursuant to its 401(k) Retirement Plan (the “Plan”).

In connection with this opinion, we have examined the Registration Statement and related Prospectus, the Company’s Certificate of Incorporation, as amended, the Bylaws and such other documents, records, certificates, memoranda and other instruments as we deem necessary as a basis for this opinion. We have assumed the genuineness and authenticity of all documents submitted to us as originals, the conformity to originals of all documents submitted to us as copies thereof, and the due execution and delivery of all documents where due execution and delivery are a prerequisite to the effectiveness thereof.

Our opinion is expressed only with respect to the federal laws of the United States of America, the General Corporation Law of the State of Delaware and the laws of the State of California. We express no opinion as to whether the laws of any particular jurisdiction other than those identified above are applicable to the subject matter hereof.

On the basis of the foregoing, and in reliance thereon, we are of the opinion that the Shares, when sold and issued in accordance with the Plan and the Registration Statement, will be validly issued, fully paid, and nonassessable.

We consent to the filing of this opinion as an exhibit to the Registration Statement.

Cooley Godward Kronish LLP
By:		/s/ Mark P. Tanoury
		Mark P. Tanoury