The British H-class submarines were Holland 602 type submarines used by the Royal Navy. The submarines constructed for the British Royal Navy between 1915 and 1919 were designed and built in response to German boats which mined British waters and sank coastal shipping with ease owing to their small size. The H class was created to perform similar operations in German waters, and to attack German submarines operating in British waters.

The Holland 602 type submarine, also known as the H-class submarine, was one of the most numerous submarines of World War I. The type was designed by the Electric Boat Co. of the United States, but most of the boats were built abroad: in Canada by the subsidiary of the British Vickers company and in British shipyards.