Pneumatic run-flat tire

A pneumatic radial tire which can run in a flat tire condition comprising: a side reinforcing layer disposed on a carcass layer of the side region and having a generally crescent sectional shape; and a belt layer composed of a belt ply in which metal wire bundles (each bundle containing untwined plural metal wires arranged in parallel) are arranged planarly in parallel to each other and being spaced from each other with a distance therebetween in the tire widthwise direction, and an inner liner has a thickness of 0.1 to 0.3 mm. The light run-flat tire can run to a safe place while supporting the load of the vehicle even if the tire is punctured so that the internal pressure thereof is lowered or even becomes zero, and can effect a comfortable ride and a low rolling resistance when it is filled with a normal internal pressure.