USS Segundo (SS-398), a Balao-class submarine, was a ship of the United States Navy named for the segundo, a cavalla fish of Caribbean waters. Segundo was laid down on 14 October 1943 by the Portsmouth Navy Yard in Kittery, Maine; launched on 5 February 1944; sponsored by Mrs. John L. Sullivan; and commissioned on 9 May 1944, Lieutenant Commander James D. Fulp, Jr., in command.