HMS Locust was a river gunboat of the Royal Navy, one of the Locust class of four gunboats, named after the locust, an insect.
Launched on 28 September 1939 and commissioned on 17 May 1940, she survived the Second World War despite being severely damaged multiple times, including taking a shell hit in Operation Overlord.
Locust had a central, but previously uninterpreted, role in Operation Jubilee, the raid on Dieppe, France in 1942. She was under the command of Commander R.E.D. Ryder VC, who had previously attacked the drydock at St. Nazaire in Operation Chariot. In recent research by Canadian Prof. David O'Keefe, the entire Dieppe raid is explained as an intelligence gathering raid specifically to capture an example of the new German 4-rotor Enigma code machine. She carried 200-odd RM commandos, which O'Keefe claims included a previously unknown group, 30 Assault Unit, as part of 40 Commando. Her shallow draft would be necessary if she was to breach the central port structures. However defensive fire was withering and the ship was unable to proceed.
She was placed in reserve from 1946 until 1951 when she was converted to a drill ship for the Royal Naval Reserve and used for training. In 1968 she was finally decommissioned and sent to the breakers.