HMS Bittern was a Bittern-class sloop of the Royal Navy. Although the last to be completed she was the name ship of her class, replacing an earlier Bittern which had been re-named before launch. Bittern was laid down on 27 August 1936 by J. Samuel White, of Cowes, Isle of Wight, launched on 14 July 1937 and completed on 15 March 1938.She served in Home waters and off the coast of Norway during the Second World War.