Disclosed is a run-flat tire having greatly increased run-flat endurance. The disclosed run-flat tire is provided with: a carcass (6) extending from a tread section (2) through a sidewall portion (3) to a bead core (5) of a bead portion (4); and a side-reinforcement rubber layer (9) that has a crescent-shaped cross-section and is disposed inside the carcass (6) in the sidewall portion (3). A heat-conducting rubber (11) having a coefficient of thermal conductivity of not less than 0.3 W/(m·K) is disposed on the inner cavity surface (12) of the tire. At least part of said heat-conducting rubber (11) is disposed in a side-reinforcement rubber layer projection area (T) where the side-reinforcement rubber layer (9) is projected onto the inner cavity surface (12) of the tire.