A locking device for an electrical charging device of a motor vehicle, in particular an electric or hybrid vehicle. The locking device is equipped with a movable bolt element, which is provided for releasably locking a charging plug in a charging socket of the electrical charging device. In addition, the movable bolt element can be moved at least into the positions “unlocked” and “locked.” Furthermore, a motor-driven drive is realized, which is provided for moving the bolt element. According to the invention, the bolt element can be moved into a third “self-locked” position beyond the “locked” position, which can be reached by means of the drive and in which unlocking is impossible without the drive.