Abstract: A Gooseneck Trailer Lock that obstructs a trailer hitch coupling mechanism and prevents the attachment to the ball of a towing vehicle. The locking device is inserted into the coupling mechanism, the slide of the coupling mechanism is moved to the closed position causing the top portion of the lock to engage the ½ inch lip on the inside of the mechanism while the body of the lock remains in the 2{fraction (5/16)} inch opening of the slide mechanism, the non-drillable barrel lock is locked and the key removed. The entire coupling mechanism is filled, preventing the insertion of the towing ball, thus preventing an unattached trailer from being attached to an unauthorized vehicle. The locking device is simple, durable, effective, and easy to use.