In order to improve a trailer coupling for motor vehicles comprising a pivot bearing body which is rigidly attached to the vehicle and upon which there is mounted a pivotal element that is pivotal about a pivotal axis, a ball neck which extends outwardly from the pivotal element and carries a coupling ball at the end thereof remote from the pivotal element, and a locking device for fixing the pivotal element relative to the pivot bearing body in interlocking manner, so that the locking device is constructed in as simple a manner as possible and can be implemented in simple manner so that it is free of play, it is proposed that the pivotal element is mounted on the pivot bearing body such that it is displaceable along the pivotal axis thereof and that by displacement of the pivotal element along the pivotal axis the pivotal element is moveable into a position wherein it is pivotal relative to the pivot bearing body and into a position wherein it is fixed relative to the pivot bearing body in mutually non-rotatable manner by means of interlocking arrangement.