USS Enaj (SP-578) was a United States Navy patrol vessel in commission from 1917 to 1918. Enaj was built as a private steam yacht of the same name by the Herreshoff Manufacturing Company at Bristol, Rhode Island, in 1909. On 11 June 1917, the U.S. Navy acquired her under a free lease from her owner for use as a section patrol vessel during World War I. She was commissioned the same day as USS Enaj (SP-578) with Ensign L. F. Herreshoff, USNRF, in command. Enaj was returned to her owner on 31 December 1918.