A motor launch (ML) is a small military vessel in British navy service. It was designed for harbour defence and submarine chasing or for armed high speed air-sea rescue.
Although small by naval standards, it was larger than the preceding Coastal Motor Boats of 40 and 55 ft length. The first motor launches entered service in the First World War. These were 580 80-foot-long (24 m) vessels built by the US Elco company for the Admiralty, receiving the designations ML-1 to ML-580. They served between 1916 and the end of the war with the Royal Navy defending the British coast from German submarines.