Moter vehicle trailer coupling

The coupling has a ball rod (1) with a shaft that can move between rest and working positions and a coupling ball (2). The shaft is held in a coupling support (3) connected to the vehicle and is secured in the working position by a locking unit. An axially adjustable transverse bolt of the locking unit is arranged transverse to the shaft of the ball rod and engages a radial recess in the shaft of the ball rod to lock the ball rod. The transverse bolt slides axially in a guiding transverse bolt in the coupling support and is spring-biased in the direction of the ball rod or the radial recess. The free end of the transverse bolt has a handle (4) to unlock the transverse bolt against the spring force and out of the recess.