A run- flat radial tire comprising: a carcass spanning between a pair of bead portions; a vehicle mounting direction outer side side-reinforcing rubber layer that is provided at a tire side portion at a vehicle mounting direction outer side and that extends in a tire radial direction along an inner face of the carcass, and a vehicle mounting direction inner side side-reinforcing rubber layer that is provided at a tire side portion at a vehicle mounting direction inner side and that extends in the tire radial direction along an inner face of the carcass, wherein a tire radial direction outer side end portion of the vehicle mounting direction inner side side-reinforcing rubber layer is closer to a tire equatorial plane than a tire radial direction outer side end portion of the vehicle mounting direction outer side side-reinforcing rubber layer, the run-flat radial tire further comprises a maximum width inclined belt layer that is provided at a tire tread portion at a tire radial direction outer side of the carcass, that includes a cord extending in a direction inclined with respect to a tire circumferential direction, and that is a belt layer having a largest width in a tire axial direction, characterised in that a tire cross section height of the run-flat radial tire is 115 mm or more than 115 mm, wherein the tire cross section height means a length of 1/2 of the difference between the tire external diameter and the rim diameter in a non-loaded state as defined in the Year Book by the Japan Automobile Tire Manufacturers Association, and an overlap width L1 in the tire axial direction between the maximum width inclined belt layer and the vehicle mounting direction outer side side-reinforcing rubber layer, and an overlap width L2 in the tire axial direction between the maximum width inclined belt layer and the vehicle mounting direction inner side side-reinforcing rubber layer are each 15% or more than 15 % of the tire axial direction width of the maximum width inclined belt layer. a carcass spanning between a pair of bead portions; a vehicle mounting direction outer side side-reinforcing rubber layer that is provided at a tire side portion at a vehicle mounting direction outer side and that extends in a tire radial direction along an inner face of the carcass, and a vehicle mounting direction inner side side-reinforcing rubber layer that is provided at a tire side portion at a vehicle mounting direction inner side and that extends in the tire radial direction along an inner face of the carcass, wherein a tire radial direction outer side end portion of the vehicle mounting direction inner side side-reinforcing rubber layer is closer to a tire equatorial plane than a tire radial direction outer side end portion of the vehicle mounting direction outer side side-reinforcing rubber layer, the run-flat radial tire further comprises a maximum width inclined belt layer that is provided at a tire tread portion at a tire radial direction outer side of the carcass, that includes a cord extending in a direction inclined with respect to a tire circumferential direction, and that is a belt layer having a largest width in a tire axial direction, characterised in that a tire cross section height of the run-flat radial tire is 115 mm or more than 115 mm, wherein the tire cross section height means a length of 1/2 of the difference between the tire external diameter and the rim diameter in a non-loaded state as defined in the Year Book by the Japan Automobile Tire Manufacturers Association, and an overlap width L1 in the tire axial direction between the maximum width inclined belt layer and the vehicle mounting direction outer side side-reinforcing rubber layer, and an overlap width L2 in the tire axial direction between the maximum width inclined belt layer and the vehicle mounting direction inner side side-reinforcing rubber layer are each 15% or more than 15 % of the tire axial direction width of the maximum width inclined belt layer.