HMS H31 was a British H class submarine built by Vickers Limited, Barrow-in-Furness.

During the war, she took part in the operation to keep the Scharnhorst in Brest, France in december 1941 before the "Channel Dash" to German homeports in the company of Gneisenau and Prinz Eugen in February 1942.

[4] The use of its electric motors made the submarine travel at 11 knots (20 km/h; 13 mph).

Post-H20 British H-class submarines had ranges of 2,985 nautical miles (5,528 km; 3,435 mi) at speeds of 7.5 knots (13.9 km/h; 8.6 mph) when surfaced.

[2] It is a Holland 602 type submarine but was designed to meet Royal Navy specifications.