HMS H31 was a British H class submarine built by Vickers Limited, Barrow-in-Furness. She was laid down on 19 April 1917 and was commissioned on 21 February 1919. HMS H31 survived until World War II. During the war, she took part in the operation to keep the German battleship Scharnhorst in Brest, France in November 1941 before the "Channel Dash" to German homeports in the company of Gneisenau and Prinz Eugen in February 1942. During the operation, H31 was sunk by unknown causes, but most believe she was mined in the Bay of Biscay on 24 December 1941.