The Class 398 Citylink is a fleet of 36 tram-train multiple units being built for Transport for Wales Rail by Swiss rolling stock manufacturer Stadler Rail.  The units will be equipped with traction battery packages, allowing them to operate over non-electrified sections of track in addition to those with 25 kV 50 Hz AC overhead supplies.

When built, Transport for Wales Rail Class 398 units will operate services on the Rhondda, Merthyr and City lines, and the Cardiff Bay Branch.