In a trailer coupling comprising a cross member which is mountable on a rear region of a vehicle body, a pivot bearing unit arranged on the cross member, by means of which a ball neck carrying a coupling ball is pivotally mounted about a pivot axis between a working position and a rest position, and a contact unit arranged on the ball neck as well as a cable harness guided from the contact unit to a vehicle-mounted cross member and provided for connecting to a vehicle electrical supply system, it is provided that a transition portion of the cable harness which runs in a movable manner relative to the ball neck and relative to the pivot bearing unit from the ball neck to an attachment point connected fixedly to the cross member forms at least one loop which extends over an end face of the pivot bearing unit extending transversely to the pivot axis and which varies in size when transferring from the working position to the rest position or vice versa.