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. Operators included the United States Navy, the Chilean Navy, the Royal Navy (33 submarines), the Imperial Russian Navy, the Soviet Navy, the Italian Regia Marina, the Royal Canadian Navy, the Royal Dutch Navy and the navy of the short-lived Ukrainian State.