A control system for an internal combustion engine is provided. In the control system, a target intake air amount is calculated according to a target output torque of the engine, and an intake air amount of the engine is controlled according to the target intake air amount. An ignition timing of the engine is controlled. The following steps 1) to 3) are repeatedly executed until a convergence time at which a difference between an estimated output torque and the target output torque becomes equal to or less than a predetermined threshold value, after setting an initial value of a temporary target intake air amount, and the target intake air amount is set to the temporary target intake air amount at the convergence time: 1) calculating an estimated retard correction amount which is a retard correction amount of the ignition timing when supplying the temporary target intake air amount of air to the engine; 2) calculating the estimated output torque of the engine according to the temporary target intake air amount and the estimated retard correction amount; and 3) modifying the temporary target intake air amount so that the estimated output torque approaches the target output torque.