Steam gun boat (SGB) was a Royal Navy term for a class of small naval vessels used during the Second World War. The class consisted of nine gun boats, powered by steam, and built from 1940 to 1942 for the Coastal Forces of the Royal Navy. They were developed in parallel with the Fairmile D motor torpedo boats ("dog boats"), specifically as a response to the need to hunt down German E-boats and also as a response to the scarcity of suitable diesel engines. While sixty were planned only an initial batch of nine were ordered on 8 November 1940, of which seven were completed.