An air ambulance was called to the scene (in the area of Bramalea City Centre near Queen Street and Central Park Drive) after the incident at about 6 a.m. Tuesday.
The woman was airlifted to a Toronto-area trauma centre with life-threatening injuries.
Peel regional police Const. Thomas Ruttan says a male suspect has been arrested following a police pursuit but had no immediate details on the suspect or possible charges.
A police cruiser was involved in a collision with another vehicle during the chase, but police say no one was hurt in the crash.
Witnesses told police the stabbing took place inside a vehicle and passersby came to the rescue of the victim, pulling her out of the car.
(CFRB, AM640, The Canadian Press)