EXHIBIT 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption “Experts” and to the use of our report dated March 28, 2007, in Amendment No. 1 to the Registration Statement (Form S-1 No. 333-148490) and the related Prospectus of Orexigen Therapeutics, Inc. for the registration of shares of its common stock.

/s/ Ernst & Young LLP  

San Diego, California
January 10, 2008