A locking device for trailer hitches of the pintle ring/hook type is disclosed to include a lower base portion with an upstanding locking eye insertable into the pintle ring. An upper lock portion containing a shank lock is mountable onto the lower base portion with the locking eye within a lock slot of the shank lock. The shank lock is then locked in position after having passed through the locking eye so as to securely lock the base and lock portions of the locking device within the pintle ring and with the locking bolt of the shank lock completely contained within the lock and not being exposed outside of the lock.