Abstract: A self-locking valve spring retainer (30) operatively retaining a return spring (28) on the stem (20) of a poppet valve (16) comprises an annular base ring (48) from which three flexible arms (52) upwardly extend. A locking step (66) projects radially inwardly from each of the arms (52) to provide an engaging ledge (70) which interlocks with a corresponding mating projection (68) of the valve stem (20). An annular waisted hinge (86) is formed between the three arms (52) and the base ring (48) to ease stresses on the retainer (30) as the arms (52) are blossomed outwardly during installation and removal. The annular base ring (48) is fabricated from a first organic polymeric material capable of deformation thus permitting the arms (52) to flex outward therefrom.