A run-flat radial tire, comprising: a carcass spanning between a pair of bead portions; an inclined belt layer that is provided at a tire radial direction outer side of the carcass, and that is configured by one or more belt plys (16A, 16B) including cord extending in a direction inclined with respect to a tire circumferential direction; a tread portion that is provided at a tire radial direction outer side of the inclined belt layer and that has a tread face formed with a plurality of circumferential direction grooves (21, 21A) extending along the tire circumferential direction; and a side reinforcing layer that is provided at a tire side portion, the tire side portion coupling the bead portion and the tread portion together, that extends along an inner face of the carcass from a side of the bead portion toward a side of the tread portion, that overlaps a belt ply having a maximum width among the one or more belt plys (16A, 16B), that has an overlap width with the maximum width belt ply along a tire width direction having a length of 20% or more of a tire cross-section height, and that has an end portion at the tread portion side that is disposed further toward a tire width direction outer side than a groove bottom of a circumferential direction groove, among the plurality of circumferential direction grooves, that is furthest toward the tire width direction outer side, characterised in that: in a cross-section along the tire width direction, the end portion at the tread portion side of the side reinforcing layer is disposed at a position separated, along the tire width direction, from an intersection point of the groove bottom and a groove wall at a tire width direction outer side of the circumferential direction groove that is furthest toward the tire width direction outer side, by 3% or more of a tread half width, in that: the tire cross-section height is 115 mm or more, and in that the overlap width is set to a length within a range from 22% to 27% of the section height. a carcass spanning between a pair of bead portions; an inclined belt layer that is provided at a tire radial direction outer side of the carcass, and that is configured by one or more belt plys (16A, 16B) including cord extending in a direction inclined with respect to a tire circumferential direction; a tread portion that is provided at a tire radial direction outer side of the inclined belt layer and that has a tread face formed with a plurality of circumferential direction grooves (21, 21A) extending along the tire circumferential direction; and a side reinforcing layer that is provided at a tire side portion, the tire side portion coupling the bead portion and the tread portion together, that extends along an inner face of the carcass from a side of the bead portion toward a side of the tread portion, that overlaps a belt ply having a maximum width among the one or more belt plys (16A, 16B), that has an overlap width with the maximum width belt ply along a tire width direction having a length of 20% or more of a tire cross-section height, and that has an end portion at the tread portion side that is disposed further toward a tire width direction outer side than a groove bottom of a circumferential direction groove, among the plurality of circumferential direction grooves, that is furthest toward the tire width direction outer side, characterised in that: in a cross-section along the tire width direction, the end portion at the tread portion side of the side reinforcing layer is disposed at a position separated, along the tire width direction, from an intersection point of the groove bottom and a groove wall at a tire width direction outer side of the circumferential direction groove that is furthest toward the tire width direction outer side, by 3% or more of a tread half width, in that: the tire cross-section height is 115 mm or more, and in that the overlap width is set to a length within a range from 22% to 27% of the section height. the tire cross-section height is 115 mm or more, and in that the overlap width is set to a length within a range from 22% to 27% of the section height.