USS Threadfin (SS-410), a Balao-class submarine, was the only ship of the United States Navy to be named for the threadfin, any of a family of fishes related to the mullets and distinguished by filamentous rays on the lower part of the pectoral fin.
Threadfin was laid down on 18 March 1944 at the Portsmouth Navy Yard in Kittery, Maine. She was launched on 26 June 1944 sponsored by Mrs. Frank G. Fox, and commissioned on 30 August 1944 with Commander John J. Foote in command.
Training and trials out of Portsmouth followed her final completion late in September. After transiting the Panama Canal in mid-November, the submarine reached Pearl Harbor early in December and conducted intensive training in preparation for her first war patrol.
After successive years of routine operations in the Caribbean Sea and Atlantic Ocean, Threadfin was placed out of commission on 18 August 1972 and transferred to Turkey that same day. She served in the Turkish Navy, on loan, as TCG 1. İnonu (S 346) until the following summer. On 1 August 1973, her name was struck from the American Naval Vessel Register. Two weeks later, the loan expired, she was returned to the United States Navy, and sold to Turkey. In mid-1998 she was still in active service in the Turkish Navy. She has reportedly been decommissioned since then.