USS D-2 (SS-18) was a D-class submarine of the United States Navy. Her keel was laid down by Fore River Shipbuilding Company in Quincy, Massachusetts, under a subcontract from Electric Boat Company of Groton, Connecticut, as Grayling, making her the first ship of the U.S. Navy to be named for the Arctic grayling, a fresh-water game fish closely related to the trout. Grayling was launched on 16 June 1909, sponsored by Miss C. H. Bowles, and commissioned on 23 November 1909 with Lieutenant Owen Hill in command. She was renamed D-2 on 17 November 1911.