HMS L4 was a British L class submarine built by Vickers, Barrow. She was laid down on 21 June 1916 and was commissioned on 26 December 1918. On 20 October 1927 off Hong Kong, HMS L4 rescued the SS Irene and her crew from a pirate attack after firing her deck gun. HMS L4 was sold on 24 February 1934 and then broken up in Charlestown, Fife.