HMS Triton was a submarine of the Royal Navy named for the son of Poseidon and Amphitrite, the personification of the roaring waters. She was the lead ship of the T class of diesel-electric submarines. Her keel was laid down on 28 August 1936 by Vickers Armstrong at Barrow-in-Furness. She was launched on 5 October 1937, and commissioned on 9 November 1938.

The Royal Navy's T class of diesel-electric submarines was designed in the 1930s to replace the O, P, and R classes. Fifty-three members of the class were built just before and during the Second World War, where they played a major role in the Royal Navy's submarine operations. Four boats in service with the Royal Netherlands Navy were known as the Zwaardvisch class.