The British submarine P.311 was the only Royal Navy T-Class submarine not to be given a name.
She was to have received the name HMS Tutankhamen but was lost before this was formally done. The Prime Minister, Winston Churchill had minuted the Admiralty on 5 November 1942, 19 December and again on 27 December, saying that all submarines should have names. In the final minute, he provided a list of suggestions and insisted that all unnamed submarines be given names within a fortnight.
P.311 was a group 3 boat built by Vickers Armstrong at Barrow-in-Furness and commissioned on 5 March 1942 under the command of Lieutenant R.D. Cayley. She was one of only two T-class submarines completed without an Oerlikon anti-aircraft gun, the other being HMS Trespasser.
She joined the 10th Submarine Flotilla at Malta in November 1942, and was lost with all hands between 30 December and 8 January 1942 whilst en route to La Maddalena, Sardinia where she was to attack two Italian 8-inch gun cruisers using Chariot human torpedoes carried on the casing as part of Operation Principle. It was assumed that she was mined.