The British Rail Class 317 is an electric multiple unit (EMU) passenger train constructed by British Rail Engineering Limited in two batches, 48 sets being produced in 1981–82 and 24 sets in 1985–87. They were the first of several classes of British Rail EMU to be based on the all-steel Mark 3 bodyshell, departing from the "PEP"-aluminium design which had spawned the earlier Class 313 to Class 315, Class 507 and Class 508. The Mark 3 bodyshell was also the basis of Class 318, Class 455, and the diesel Class 150. The Class 317 uses overhead alternating current electrification.

Each unit is composed of four vehicles: two unpowered standard-class vehicles with driver's cabs, an intermediate trailer with both first- and standard-class seating, and an intermediate motor vehicle with second-class seating. The motor vehicle also carries the roof-mounted Stone Faiveley AMBR pantograph.

The technical description of the formation of the units is DTSO(A)-MSO-TCO-DTSO(B)

DTSO vehicle 77092 from unit 317345 is preserved at the East Anglian Railway Museum, and TCO vehicle 71621 from the same unit is at The Depot in Caxton. It will be a static display and it will be used to tell the story of the British Railways class 317's as well as the history of electrification in Anglia.