HMS Tuna (N94) was a T-class submarine of the Royal Navy. She was laid down by Scotts, Greenock and launched on 10 May 1940. She was equipped with German-built MAN Diesel engines and spent her career in World War II in western European waters, in the North Sea and off the west coast of France, and most famously taking part in Operation Frankton.

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.