USS G-2 (SS-27) was a G-class submarine of the United States Navy. While the four G-boats were nominally all of a class, they differed enough in significant details that they are sometimes considered to be four unique boats, each in a class by herself. G-2 was named Tuna when her keel was laid down on 20 October 1909 by the Lake Torpedo Boat Company in Bridgeport, Connecticut, making her the first ship of the United States Navy to be named for the tuna, a large, vigorous, spiny-finned fish highly esteemed for sport and food. She was renamed G-2 on 17 November 1911, launched on 10 January 1912 sponsored by Ms. Marjorie F. Miller, towed to the New York Navy Yard after the termination of the Lake contract on 7 November 1913 where she was completed, and commissioned on 1 December 1913 with Lieutenant, junior grade Ralph C. Needham in command.