A control system for an internal combustion engine having a throttle valve disposed in an intake passage of said engine, comprising: rotational speed detecting means for detecting a rotational speed of said engine; target output torque calculating means for calculating a target output torque of said engine; target intake air amount calculating means including exhaust gas recirculation ratio calculating means for calculating an exhaust gas recirculation ratio of said engine, for calculating a target intake air amount of said engine using the target output torque and the exhaust gas recirculation ratio; and control means for controlling said engine using the target intake air amount, wherein said exhaust gas recirculation ratio calculating means includes: intake pressure estimating means for estimating an intake pressure of said engine; wide-open intake air amount calculating means for calculating a wide-open intake air amount according to the engine rotational speed, the wide-open intake air amount being an intake air amount corresponding to a state where said throttle valve is fully opened; and theoretical intake air amount calculating means for calculating a theoretical intake air amount according to the wide-open intake air amount and the intake pressure, the theoretical intake air amount being an intake air amount corresponding to a state where no exhaust gas of said engine is recirculated to a combustion chamber of said engine, wherein said exhaust gas recirculation ratio calculating means calculates the exhaust gas recirculation ratio using the theoretical intake air amount and the target intake air amount. rotational speed detecting means for detecting a rotational speed of said engine; target output torque calculating means for calculating a target output torque of said engine; target intake air amount calculating means including exhaust gas recirculation ratio calculating means for calculating an exhaust gas recirculation ratio of said engine, for calculating a target intake air amount of said engine using the target output torque and the exhaust gas recirculation ratio; and control means for controlling said engine using the target intake air amount, wherein said exhaust gas recirculation ratio calculating means includes: intake pressure estimating means for estimating an intake pressure of said engine; wide-open intake air amount calculating means for calculating a wide-open intake air amount according to the engine rotational speed, the wide-open intake air amount being an intake air amount corresponding to a state where said throttle valve is fully opened; and theoretical intake air amount calculating means for calculating a theoretical intake air amount according to the wide-open intake air amount and the intake pressure, the theoretical intake air amount being an intake air amount corresponding to a state where no exhaust gas of said engine is recirculated to a combustion chamber of said engine, wherein said exhaust gas recirculation ratio calculating means calculates the exhaust gas recirculation ratio using the theoretical intake air amount and the target intake air amount. intake pressure estimating means for estimating an intake pressure of said engine; wide-open intake air amount calculating means for calculating a wide-open intake air amount according to the engine rotational speed, the wide-open intake air amount being an intake air amount corresponding to a state where said throttle valve is fully opened; and theoretical intake air amount calculating means for calculating a theoretical intake air amount according to the wide-open intake air amount and the intake pressure, the theoretical intake air amount being an intake air amount corresponding to a state where no exhaust gas of said engine is recirculated to a combustion chamber of said engine, wherein said exhaust gas recirculation ratio calculating means calculates the exhaust gas recirculation ratio using the theoretical intake air amount and the target intake air amount.