HMS Janus, named after the Roman god, was a Javelin or J-class destroyer of the Royal Navy.

She was ordered from the Swan Hunter & Wigham Richardson Limited at Wallsend-on-Tyne as part of the 1936 Build Programme and laid down on 29 September 1937, launched on 10 November 1938 and commissioned on 5 August 1939.

[1] Off Namsos, Norway, on 30 April 1940 the sloop Bittern was mistaken for a cruiser and was badly damaged by German Junkers Ju 87 dive bombers and had to be sunk by Janus.

[2] On 23 January 1944 Janus was struck by one Fritz X guided bomb dropped by a German He 111 torpedo bomber and sank off the Anzio beachhead in western Italy (according to another version, she was sunk by Henschel Hs 293 glider bomb or a conventional torpedo – see Fritz X article).

It was recorded that during her last duty Janus had laid down nearly 500 salvos of 4.7-inch shells in the first two days of the landings in support of allied troops.