A half thrust bearing having a semicircular ring shape for receiving an axial force of a crankshaft of an internal combustion engine is provided. The half thrust bearing includes thrust reliefs formed adjacently to end surfaces on both sides in a circumferential direction on a slide surface side which receives the axial force so that wall thicknesses become thinner toward the end surfaces. The thrust relief on a rear side in a rotational direction of the crankshaft or both thrust reliefs are formed so that a length of the thrust relief in an inner end portion in a radial direction of the half thrust bearing is longer than a length of the thrust relief in an outer end portion in the radial direction of the half thrust bearing.