HMS H8 was a British H-class submarine built by the Canadian Vickers Co., Montreal.

Like other Canadian-built submarines, she was sailed across the Atlantic for service in the North Sea and as recognition of this she initially remained under the command of her Canadian captain, Lieutenant-Commander B. L. Johnson, R.N.R.

British H-class submarines had ranges of 1,600 nautical miles (3,000 km; 1,800 mi) at speeds of 10 knots (19 km/h; 12 mph).

[1] H8 was fitted with a 6 pounds (2.7 kg) Hotchkiss quick-firing gun (6-pounder) and four 18 inches (460 mm) torpedo tubes.

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