The invention relates to a steering antitheft device for an automobile, said device comprising an antitheft body including: a first portion (1) housing a locking means comprising a bolt (4) movably mounted between a non-lockout position, in which the bolt is remotely located from the steering column, and a lockout position in which the bolt blocks said column, a bolt driving slider (10) capable of driving the bolt (4) into a lockout or non-lockout position, and a second portion (2) in which a latch (20) capable of controlling the movement of the slider (10) is to be inserted and secured, characterised in that said second portion (2) is made of a material having a density lower than the density of the material of the first portion (1), and in that said first portion (1) includes a super-lockout means arranged so as to block the bolt (4) in a lockout position in the event the second portion (2) is pulled apart.