An ignition timing control system for an internal combustion engine in which the ignition timing is kept at a retarded constant level within a lower engine speed range and a higher engine speed range and is kept at an advanced constant level within a middle engine speed range. Within transitional engine speed ranges between the lower and middle engine speed ranges and between the middle and higher engine speed ranges, the ignition timing is changed generally proportionate to and inversely proportionate to the instantaneous engine speed, respectively.