Abstract: Disclosed are two embodiments (40, 50) of a self-locking prevailing torque fastener featuring a common base portion (2) having an aperture (4) therethrough for receiving a threaded member that is at least partially surrounded by means such as a warped helical edge (6) for engaging the threads of the threaded member. Fasteners (40, 50) are provided with a pair of spaced-apart resilient torque arms having respective sections (8) that respectively extend downwardly from opposite edge of base portion (2) to sections (10) that extend upwardly to sections (12) that extend through respective openings (14) in each to respective free-ends (16) that are adapted to press against opposite sides of the threaded member.