Abstract: An anti-theft device for automobile vehicles of the type comprising a lock having a barrel actuated by a key. A locking bolt member is provided extending longitudinally of the barrel and the barrel has a cam profile cooperating with the bolt member for shifting the latter in a direction parallel to the axis of the barrel. The bolt member is extended by a stem which is floatably mounted so as to be transversely pivotable with respect to the axis of the bolt member. The stem is provided with a tab cooperating with a cam profile integral with the barrel, the cam controlling its transverse displacement. The stem has at the end opposed to the bolt member a transverse nose portion adapted to be cooperable with a radial recess in the body of the anti-theft device. Elastically yieldable means bias the nose portion toward the recess and a radially movable push-member is disposed in the bottom of the recess and is elastically biassed outwardly of the recess.