Trailer coupling system for motor vehicles

The invention relates to a trailer coupling for a motor vehicle, in particular for a passenger car, with a bearing module (11; 111) that has a bearing base (12; 112) arranged on a support (19; 119) to be fastened to a rear of the motor vehicle, and a bearing element (13; 113) movably mounted on the bearing base (12; 112), on which a coupling carrier with a coupling element (31) for coupling a trailer or load carrier is arranged, wherein the bearing module (11; 111) supports the coupling carrier between an operating position (B), in which the coupling element (31) for coupling a trailer or a load carrier projects in front of the rear of the motor vehicle, and a non-use position (N), in which the coupling element (31) is adjusted toward the rear of the motor vehicle, in particular is arranged behind a bumper, wherein a drive for actuating a locking device (14) of the coupling element (31) is provided at least in the operating position or for adjusting the coupling element (31) between the non-use position (N) and the operating position. The bearing module (11; 111) forms a base module for a modular building block system (10). The bearing element (13; 113) has a coupling carrier mounting interface (21) for the coupling carrier, which is designed for optional mounting of a coupling carrier of a first type or a coupling carrier of at least a second type, which differs from the coupling carrier of the first type.