Abstract: The present invention provides for a tamperproof bottle locking system, comprising a flanged outer cap apparatus having a pair of pivoted semicircular arm members that when fully closed beneath the protruding circumferential neck ring of a bottle and locked with a detachable lock, by passing the unhinged end of a U-shaped shackle of the lock through the end holes of the arm members, swiveling it closed, and snapping it shut, securely locks the outer cap device of the present invention, preventing its removal, thereby protecting the contents of the bottle from being tampered with.