GWR 3501 Class

The GWR 3501 Class was a series of 2-4-0 and 2-4-0T mixed-traffic and suburban passenger locomotives built for the Great Western Railway from 1885 under William Dean's superintendency, designed for the secondary passenger and light mixed-traffic duties across the GWR's diverse network of main and branch lines in the West of England, South Wales, and the Midlands. The class used both tender and tank variants of the 2-4-0 configuration, reflecting the GWR's practice of building related tender and tank locomotive types for different aspects of the same traffic requirements.

Dean designed the 3501 Class as part of his broader programme of providing the GWR with a standardised range of secondary passenger and mixed-traffic types to replace the varied collection of locomotives inherited from the pre-Armstrong era. The 2-4-0 wheel arrangement was still appropriate for the secondary and branch passenger work the class was designed to handle, where the leading single axle provided adequate guidance at moderate speeds and the two coupled driving wheels gave sufficient adhesion for light passenger trains on the GWR's rural and secondary lines.

The 3501 Class gave service through the late Victorian and Edwardian periods before being superseded by Dean's own 4-4-0 designs and subsequently Churchward's more modern types. None was preserved.