King pin with sensor device

The present invention relates to a kingpin (40) for attachment to a semi-trailer (10). The disclosed kingpin (40) has a pin body (41) which can be releasably engaged with a tractor-side fifth wheel coupling and a sensor device (60; 160; 260) for detecting driving states of the semi-trailer (10). The sensor device (60; 160; 260) is arranged on the pin body (41) and is designed to detect a driving state of the semi-trailer (10).