Police said the collision happened around 7 p.m. on Finch Ave. E., when a Nissan Pathfinder SUV tried to turn across two lanes of traffic onto Seneca Hill Drive and collided with an oncoming Nissan Maxima.
The Maxima then left the road and struck a 25-year-old female pedestrian who was in the southeast area of the intersection.
The pedestrian suffered life-threatening injuries and was rushed to hospital.
Police allege the Pathfinder's driver abandoned their vehicle and fled the scene on foot.
The 46-year-old driver of the Maxima remained at the scene.
Police are urging anyone who witnessed the collision to contact them.