Tow bar with a vehicle contact unit

A trailer coupling (10) with a coupling arm (20), wherein the coupling arm can be fastened to a vehicle mount (50) by means of a plug connection having a plug projection (21) and a plug receptacle (52), wherein the trailer coupling (10) has a fixing device (40) in which form-locking contours (38, 58) arranged on the vehicle mount (50) and the coupling arm next to the plug projection (21) and the plug receptacle (52) engage with one another, wherein an electrical vehicle contact unit (70) with connection contacts (71) for connecting the trailer is arranged on the coupling arm (20), which has at least one connection line (80) for connection to an on-board electrical system (93) of the motor vehicle (90). Electrical contact elements (100, 101, 150, 151) are arranged on the form-locking contours (38, 58), which in the operating position (G) of the coupling arm (20) are in contact with one another and connect an on-board electrical system section (81) intended for connection to the on-board electrical system (93) and a contact unit section (82) connected to the vehicle contact unit (70) of an electrical connection line (80) with one another.