A removable anti-theft device for a coupler, said coupler comprising a coupling head mounted on a trailer and having a cavity intended to receive in a coupled position a coupling ball, having a shape complementary to the cavity, mounted on a towing vehicle to secure said trailer and said vehicle, said anti-theft device including: - two half-shells (2, 2'), articulated via hinges (21, 21'), capable, on the one hand, when abutted against each other, in a closed position, of forming an anti-theft case, configured to grip said coupling head, and optionally said coupling ball fastened on the towing vehicle, and on the other hand, when spaced apart from each other by rotation around the hinges (21, 21'), of taking an open position allowing the removal of the anti-theft device from said coupling head, - a locking means configured to block the two half-shells (2, 2') in the first closed position with a padlock having a portion for receiving a key and a handle, - each half-shell (2, 2') is equipped with a fastening tab (22, 22'), each fastening tab (22, 22') including a bore (23, 23'), the bores (23, 23') being intended to meet facing each other when the two half-shells (2, 2') are in said closed position, characterised in that - the anti-theft device includes a fairing fastened on a wall of one of the two half-shells (2, 2'), said fairing forming with said wall of the half-shell a housing, the housing receiving the padlock, and maintaining the padlock in a position such that, in said closed position of the two half-shells (2, 2'), said handle can be actuated by means of a key received in said portion for receiving a key of the padlock, in order to switch from an unlocked position, wherein it is retracted by at least one of the bores (23, 23') facing the fastening tabs (22, 22') to a locked position, wherein said handle passes through the two bores (23, 23') facing the fastening tabs (22, 22'). - two half-shells (2, 2'), articulated via hinges (21, 21'), capable, on the one hand, when abutted against each other, in a closed position, of forming an anti-theft case, configured to grip said coupling head, and optionally said coupling ball fastened on the towing vehicle, and on the other hand, when spaced apart from each other by rotation around the hinges (21, 21'), of taking an open position allowing the removal of the anti-theft device from said coupling head, - a locking means configured to block the two half-shells (2, 2') in the first closed position with a padlock having a portion for receiving a key and a handle, - each half-shell (2, 2') is equipped with a fastening tab (22, 22'), each fastening tab (22, 22') including a bore (23, 23'), the bores (23, 23') being intended to meet facing each other when the two half-shells (2, 2') are in said closed position, characterised in that - the anti-theft device includes a fairing fastened on a wall of one of the two half-shells (2, 2'), said fairing forming with said wall of the half-shell a housing, the housing receiving the padlock, and maintaining the padlock in a position such that, in said closed position of the two half-shells (2, 2'), said handle can be actuated by means of a key received in said portion for receiving a key of the padlock, in order to switch from an unlocked position, wherein it is retracted by at least one of the bores (23, 23') facing the fastening tabs (22, 22') to a locked position, wherein said handle passes through the two bores (23, 23') facing the fastening tabs (22, 22').