A stop control system for an internal combustion engine, which controls a stop position of a piston of the engine to a predetermined position during stoppage of the engine by controlling an intake air amount, comprising: an intake air amount-adjusting valve for adjusting the intake air amount; rotational speed-detecting means (2, 24) for detecting a rotational speed of the engine; intake air amount control means (2, 13b) for controlling said intake air amount-adjusting valve toward a closed side when a command for stopping the engine is issued, and thereafter when the detected rotational speed of the engine becomes lower than a stop control start rotational speed (NEICOFREFN), controlling (S42, S46) said intake air amount-adjusting valve toward an open side; characterized in that the control system furthermore comprises: final compression stroke rotational speed-obtaining means adapted to obtain the rotational speed of the engine at a predetermined timing in a final compression stroke which is the last compression stroke in a cylinder before the engine is stopped, as a final compression stroke rotational speed (NEPRSFTGT); correlation determining means adapted to determine a correlation between the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT), based on the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT) obtained (S36, S66) when said intake air amount-adjusting valve has been controlled previously toward the open side based on the stop control start rotational speed (NEIGOFTH); and target stop control start rotational speed-setting means adapted to set (S6, S9, S11) a target stop control start rotational speed (NEICOFREFX) that serves as a target of the stop control start rotational speed (NEIGFOFTH), based on the determined correlation and a predetermined final compression stroke rotational speed (NENPFLMTO) for stopping the piston at the predetermined position. an intake air amount-adjusting valve for adjusting the intake air amount; rotational speed-detecting means (2, 24) for detecting a rotational speed of the engine; intake air amount control means (2, 13b) for controlling said intake air amount-adjusting valve toward a closed side when a command for stopping the engine is issued, and thereafter when the detected rotational speed of the engine becomes lower than a stop control start rotational speed (NEICOFREFN), controlling (S42, S46) said intake air amount-adjusting valve toward an open side; characterized in that the control system furthermore comprises: final compression stroke rotational speed-obtaining means adapted to obtain the rotational speed of the engine at a predetermined timing in a final compression stroke which is the last compression stroke in a cylinder before the engine is stopped, as a final compression stroke rotational speed (NEPRSFTGT); correlation determining means adapted to determine a correlation between the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT), based on the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT) obtained (S36, S66) when said intake air amount-adjusting valve has been controlled previously toward the open side based on the stop control start rotational speed (NEIGOFTH); and target stop control start rotational speed-setting means adapted to set (S6, S9, S11) a target stop control start rotational speed (NEICOFREFX) that serves as a target of the stop control start rotational speed (NEIGFOFTH), based on the determined correlation and a predetermined final compression stroke rotational speed (NENPFLMTO) for stopping the piston at the predetermined position. final compression stroke rotational speed-obtaining means adapted to obtain the rotational speed of the engine at a predetermined timing in a final compression stroke which is the last compression stroke in a cylinder before the engine is stopped, as a final compression stroke rotational speed (NEPRSFTGT); correlation determining means adapted to determine a correlation between the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT), based on the stop control start rotational speed (NEIGOFTH) and the final compression stroke rotational speed (NEPRSFTGT) obtained (S36, S66) when said intake air amount-adjusting valve has been controlled previously toward the open side based on the stop control start rotational speed (NEIGOFTH); and target stop control start rotational speed-setting means adapted to set (S6, S9, S11) a target stop control start rotational speed (NEICOFREFX) that serves as a target of the stop control start rotational speed (NEIGFOFTH), based on the determined correlation and a predetermined final compression stroke rotational speed (NENPFLMTO) for stopping the piston at the predetermined position.