HMS Terrapin was a British submarine of the third group of the T class. She was built as P323 by Vickers Armstrong, Barrow and launched on 31 August 1943. So far she has been the only ship of the Royal Navy to bear the name Terrapin, after the animal of that name. Apart from a brief period in home waters off the Scandinavian coast, Terrapin served in the Far East for much of her wartime career.