PISTON RING

An outer circumferential surface of a piston ring has a cut surface forming a notched portion between an outer circumferential end surface and a lower surface, the cut surface including a first surface between the outer circumferential end surface and a bottom portion, and a second surface between the bottom portion and the lower surface. The second surface is inclined away from a central axis of the piston ring as it extends toward a crank chamber side, an angle of inclination of the second surface with respect to the bottom portion being greater than or equal to 50° and less than or equal to 85°. When an axial width of the piston ring is h1 and a distance in an axial direction between a connecting portion between the cut surface and the outer circumferential end surface and a connecting portion between the cut surface and the lower surface is H, H/h1 is greater than or equal to 0.2 and less than or equal to 0.4.