A handgun and a locking device for a handgun are disclosed, which handgun includes a housing, a magazine-receiving space in the housing, a slide movable in the housing, and a trigger mechanism; the locking device includes a locking body to be inserted in the magazine-receiving space, the locking body at least partially being shaped like a magazine and including a releasable catch engaging in the magazine-receiving space when the locking body is in its inserted state, and cooperating with an eccentric provided in the locking body.