The Great Western Railway (GWR) 6400 Class is a class of 0-6-0 pannier tank steam locomotive introduced by Charles Collett in 1932. All 40 examples were 'auto-fitted' – equipped with the remote-control equipment needed for working autotrains.

The 1936 GWR 7400 Class was a similar class, without the autotrain apparatus, but with a higher boiler pressure of 180 psi, providing a small but useful increase in power. An initial build of 30 in 1936-1937 was added to by British Railways in two batches each of ten locos in 1948 and 1950. These were destined for a short life, the briefest being only nine years. A minor visual difference between the 5400 and earlier 6400, and the later series of 6400, with the 7400 classes was at the join between cab and bunker. The 5400 and early 6400 had an arc whereas the later 6400 and the 7400 class was straight.

There were 40 locomotives in the 6400 Class, and 50 locomotives in the 7400 Class. Three of the 6400 Class have survived to preservation, unfortunately none of the 7400 Class survived