The Great Western Railway 4000 or Star were a class of 4-cylinder 4-6-0 passenger steam locomotives designed by George Jackson Churchward for the Great Western Railway (GWR) in 1906 and introduced from early 1907. The prototype was built as a 4-4-2 Atlantic (but converted to 4-6-0 during 1909). They proved to be a successful design which handled the heaviest long-distance express trains, reaching top speeds of 90 mph (145 km/h), and established the design principles for GWR 4-cylinder classes over the next twenty-five years.