A device for locking a motor vehicle steering shaft against rotation by means of a locking bolt which cooperates with locking recesses of the steering shaft and which can be displaced back and forth, between a locking position and a release position by means of a control member which can be rotated to-and-fro by an electric motor and which cooperates with a rotary position detector. To maintain the device as compact as possible, the control member is shaped as a circular control disk which cooperates on one side with the locking bolt and on the other side with the rotary position detector.