Abstract: A self-retaining locking assembly for threaded couplings. An externally threaded bolt rod end bearing is threadedly secured to a nut or internally threaded piston rod. The bearing includes an axially extending keyway along the threads, and the piston rod includes a circumferential groove at the mating end as well as radially extending slots in the mating face. An annular lock member has a lug projecting radially inwardly of the central aperture for engaging the keyway, and ribs and clips for mating with the radial slots and annular groove, respectively, when the rod is threaded upon the bearing. The lock member therefore cannot rotate relative to the bearing, and the piston rod cannot rotate relative to the lock member whereby the entire assembly is secured together in fixed relationship.