The London and North Western Railway (LNWR) Class G1 was a class of 0-8-0 steam locomotives. It was a superheated version of the LNWR Class G with 8 inch piston valves. The prototype was rebuilt in 1912 from a member of Class G and a further 170 new locomotives were built between 1912 and 1918. In addition, 278 older locomotives were rebuilt to the G1 specification between 1917 and 1934.