The Sûreté du Québec is not identifying the woman.
A passerby flagged the burning car on Monday morning just before 5 a.m. near the intersection of Jean-Guyon and Michel-Bohec Streets.
Firefighters discovered the corpse after they put out the fire.
It's too early to say whether the death is suspicious, said SQ Sgt. Benoît Richard.
"Right now, we don't know the cause of death," Richard said. "We're not taking any chances and we're doing a complete investigation."
The area was closed off as investigators, including a canine unit, were brought to the scene to gather evidence.