A run- flat radial tire comprising: a carcass spanning between a pair of bead portions ; a side reinforcement layer provided to tire side portions that respectively couple between the bead portions and a tread portion ; a reinforcement cord layer that is provided at a tire radial direction outside of the carcass , that comprises cord inclined to a tire circumferential direction at an angle of inclination of from 60 degrees to 90 degrees, the reinforcement cord layer being laid up at both end portions of the tread portion alone; and an inclined belt layer that is provided further to the tire radial direction inside of the tread portion than the reinforcement cord layer , characterised in that : the tire further comprises a cap layer laid up at the tire radial direction outside of the inclined belt layer , the cap layer covering the inclined belt layer entirely; the reinforcement layer is laid up at the tire radial direction outside of the cap layer ; the reinforcement cord layer is disposed such that, when the side reinforcement layer is projected along a tire radial direction, an overlap width of the reinforcement cord layer overlapping with the side reinforcement layer is a length of 7.5% of a tire section height, or greater; and the inclined belt layer is inclined to the tire circumferential direction with an angle of inclination of from 15 degrees to 30 degrees. a carcass spanning between a pair of bead portions ; a side reinforcement layer provided to tire side portions that respectively couple between the bead portions and a tread portion ; a reinforcement cord layer that is provided at a tire radial direction outside of the carcass , that comprises cord inclined to a tire circumferential direction at an angle of inclination of from 60 degrees to 90 degrees, the reinforcement cord layer being laid up at both end portions of the tread portion alone; and an inclined belt layer that is provided further to the tire radial direction inside of the tread portion than the reinforcement cord layer , characterised in that : the tire further comprises a cap layer laid up at the tire radial direction outside of the inclined belt layer , the cap layer covering the inclined belt layer entirely; the reinforcement layer is laid up at the tire radial direction outside of the cap layer ; the reinforcement cord layer is disposed such that, when the side reinforcement layer is projected along a tire radial direction, an overlap width of the reinforcement cord layer overlapping with the side reinforcement layer is a length of 7.5% of a tire section height, or greater; and the inclined belt layer is inclined to the tire circumferential direction with an angle of inclination of from 15 degrees to 30 degrees. the tire further comprises a cap layer laid up at the tire radial direction outside of the inclined belt layer , the cap layer covering the inclined belt layer entirely; the reinforcement layer is laid up at the tire radial direction outside of the cap layer ; the reinforcement cord layer is disposed such that, when the side reinforcement layer is projected along a tire radial direction, an overlap width of the reinforcement cord layer overlapping with the side reinforcement layer is a length of 7.5% of a tire section height, or greater; and the inclined belt layer is inclined to the tire circumferential direction with an angle of inclination of from 15 degrees to 30 degrees. <EOS>