Abstract: A fifth wheel coupling for mounting on a towing vehicle and for coupling to a trailer king pin, comprising a coupling plate, a pair of jaws operatively connected to the plate and having opposing king pin receiving recesses with their centers forwardly of the axis of rotation of the jaws and having faces forming a rearwardly directed recess when the jaws are closed, a locking plunger movable with respect to the plate and urged into the recess, a trip member mounted on the plate and urged to maintain the plunge in an inoperative position out of said recess and trippable by closing movement of at least one of the jaws, a locking block movable with respect to the plate and plunger from an inoperative position to an operative position in which it prevents movement of the plunger out of the recess, and an actuating member mounted on the plate and movable, by movement of the block to its inoperative position, to move the plunger out of the recess to free the jaws.