HMS H1 was a H-class submarine built by Canadian Vickers Co., Montreal for the British Royal Navy.

H1 crossed the Atlantic from St. John's, Newfoundland to Gibraltar escorted by the armed merchant cruiser HMS Calgarian.

British H-class submarines had ranges of 1,600 nautical miles (2,963 km; 1,841 mi).

[2] H1 was fitted with a 6-pounder (2.7 kg) Hotchkiss quick-firing gun and four 18-inch (457 mm) torpedo tubes.

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