HMS Unbeaten was a U-class submarine, of the second group of that class, built by Vickers Armstrong, Barrow-in-Furness.

[1] Unbeaten also lightly damaged the Italian merchant Vettor Pisani on 16 March 1942.

[1] After a refit in Chatham, and subsequent workup, Unbeaten was attached to the Third Submarine Flotilla in Scotland.

Having sailed from Holy Loch on her last patrol, Unbeaten completed Operation Bluestone, landing an agent in Spain near Bayona.

It is believed that she was probably attacked and sunk in error by a Royal Air Force Wellington of No.