Abstract: A self-aligning piston assembly has a piston member having a sidewall for slidable displacement within a bore, the piston member having an inner curved surface, the piston assembly having an inner race member having means to attach to a connecting member, the inner race member having a curved surface complimentary to the inner curved surface and, an elastomer member disposed therebetween substantially in the form of a sphere to provide a spherical type mounting of the piston to the connecting member. Utilizing a spherical type mounting, axial rigidity is maintained yet any side loading which acts through the connecting member or manufacturing tolerances are absorbed through the spherical elastomer to prevent misalignment or cocking of the piston within the bore during stroking. Utilizing the invention, excessive wear and fluid leakage by the piston is avoided since misalignment is absorbed by the elastomer member.