British Rail 18000 was a prototype mainline gas turbine-electric locomotive built for British Railways in 1949 by Brown, Boveri amp; Cie. It had, however, been ordered by the Great Western Railway in 1946, but construction was delayed due to World War II. It spent its working life on the Western Region of British Railways, operating express passenger services from London Paddington station.

No. 18000 was of A1A-A1A wheel arrangement and its gas turbine was rated at 2,500 hp (1,900 kW). It had a maximum speed of 90 miles per hour (145 km/h) and weighed 115 long tons (117 t). It was painted in BR black livery, with a silver stripe around the middle of the body and silver numbers.

It proved a troublesome machine in service. Ash from the heavy fuel oil damaged the turbine blades, and the combustion chamber liner required frequent replacement due to damage.