A trailer hitch security system for blocking access to a trailer hitch, includes a breach-resistant enclosure within which is positioned hitch engagement means (such as a hitch ball). A locking rod is configured for extending through orifices formed in the enclosure, for reversibly locking into position, and, when in-place, preventing removal of any engaged trailer hitch. Shrouds surround the orifices to prevent access to the termini of the locking rod to further impede tampering or attempted removal of the locking rod.