Police were called to the Brickyard Way and Main Street area around 2:20 p.m. to respond to report of a pedestrian who was struck.
The pedestrian, an 83-year-old woman, was taken to hospital with serious but non-life-threatening injuries.
The driver fled the scene, police said.
The driver is described as a black woman, possibly in her 20s, with loose braids. The car is described as a dark-coloured Honda Accord-type of vehicle, with damage to the driver’s side.
Police are asking anyone who was in the area around the time of the incident to contact them.
Meanwhile, Main Street is closed northbound at Williams Parkway and southbound at Gillingham Drive for the investigation. Police are asking travellers to use alternate routes.
GO buses routes 31, 33, 37 are detouring due to the road closure. Some stops are being missed, GO Transit said.