HMS H33 was a British H class submarine built by Cammell Laird, Birkenhead.

In March 1937 the submarine navigated the Gloucester and Sharpness Canal in the company of H49 whose commander had arranged the trip.

[1] During Warship Week March 1942 H33 was adopted by East Dean RDC (Gloucestershire).

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.