The British Rail Class 321 are electric multiple unit (EMU) passenger trains built by British Rail Engineering Limited's Holgate Road carriage works in three batches between 1988 and 1991. The class uses alternating current (AC) overhead electrification. The design was successful and led to the development of the similar Class 320 and Class 322. Today the class is operated by Greater Anglia. Some have been converted to Class 320 and are operated by ScotRail.