Abstract: A hitch pin assembly for connecting a hitch of a towing vehicle (e.g. an agricultural tractor) with a tongue of a towed vehicle (e.g. an agricultural implement) includes a coupling pin having a pinhead and handle at its upper end. The coupling pin is inserted through the hitch and tongue, and is held in place by a collar, which is connected to the lower end of the coupling pin. The collar and the pin are locked together by a locking mechanism which includes a pair of L shaped channels at the lower end of the coupling pin, a pair of locking pins carried by the collar which cooperate with the channels, and a bias spring carried on the collar. The bias spring provides an axial bias force which holds the locking pins in locking seat portions of the channels during normal use.