The GWR 1400 Class is a class of steam locomotive designed by the Great Western Railway for branch line passenger work. It was originally classified as the 4800 Class when introduced in 1932 and renumbered in 1946. Although credited to Charles Collett, the design dated back to 1868 with the introduction of the George Armstrong 517 class.

The 4800 Class was designed as a more modern version of the 517 Class, which were by then beginning to show their relative age. The first locomotive, No. 4800, was built by Swindon Works and entered service in 1932, with a further seventy-four engines of this type following up to 1936. During this period, Swindon also built twenty 5800 Class engines, which were broadly similar, but which were not fitted with auto-train equipment, or the Swindon top feed as later fitted to a number of 4800 class engines.

The 4800 Class locomotives retained their original numbers until the GWR decided to experimentally convert twelve 2800 Class 2-8-0s for oil-firing. It was decided that the converted engines would be reclassified as the 4800 Class and so the 75 tank locomotives already carrying this designation were reclassified as the 1400 Class with running numbers 1400-1474. The engines did not revert to their original classification after the experiment ended in 1948. They could reach a maximum speed of 80 mph which was much faster than the diesel railcars designed to replace them could reach.

75 were built, 4 have been preserved