Abstract: A locking fastener assembly for axle bearings and the like is free spinning during tightening and removal and is positively held against rotation after installation. The assembly is engageable with an axially slotted male threaded member and includes a nut with female threads and a flange end. A retainer washer includes spaced fingers formed around the nut flange for rotatably supporting the washer at the flanged end of the nut. The washer includes a tab received in the slot of the male threaded member permitting the nut to move axially but not to rotate on the male threaded member. When the nut is engaged by a wrench, the wrench releases a flexible and resilient locking clip to permit the nut freely to rotate. After the assembly has been threaded onto the male threaded member, removal of the wrench frees the locking clip and a lock finger is received in a space between fingers of the retainer washer positively to prevent further rotation of the nut.