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. In 2011 it was reported that the ship has started to leak oil and contained roughly 200,000 litres (44,000 imp gal; 53,000 US gal) of oil.