USS H-6 (SS-149) was an H-class submarine that served in the United States Navy from 1918-1931. The Imperial Russian Navy ordered 18 H-class submarines from the Electric Boat Company in 1915. Eleven were delivered, and served as the American Holland class submarines, but shipment of the final six was held up pending the outcome of the Russian Revolution of 1917, and the boats were stored in knockdown condition at Vancouver, British Columbia. All six were purchased by the U.S. Navy on 20 May 1918 and assembled at Puget Sound Navy Yard.