A catalyst overheat prevention apparatus has a temperature obtaining portion that estimates a convergence temperature of a catalyst provided in the exhaust system of an internal combustion engine and the present temperature of the catalyst. The catalyst overheat prevention apparatus also has a fuel increment calculation portion, a comparison portion, a correction portion, and a fuel increment setting portion, which are used to execute OT fuel increase control when the convergence temperature and present catalyst temperature obtained by the temperature obtaining portion are equal to or higher than an OT determination temperature. The catalyst overheat prevention apparatus also has a present temperature correction portion that corrects the present catalyst temperature to be equal to the OT determination temperature when the present catalyst temperature is equal to or higher than the OT determination temperature and the convergence temperature is equal to the OT determination temperature.