The Great Western Railway (GWR) 1366 Class was a class of 0-6-0 pannier tank steam locomotives built in 1934. They were a useful design and because of their light weight and short wheelbase and were often used on dockside branches or other lines with sharp curvatures.

The 1366 class was one of only two pannier tank designs built by the GWR that utilised outside cylinders, although various existing engines inherited by the GWR had pannier tanks and outside cylinders. The 1366 class was developed from the 1361 Class but differed by including a pannier tank rather than a saddle tank, Belpaire firebox, etc. They were designed to replace the 1392 Class.

6 were built, 1 has been preserved