Orillia OPP are currently investigating the cause of a vehicle rollover in Ramara Township.
This morning, police were called to the scene of the collision on County Road 46 just north of Highway 12.
A 21-year-old man from Selkirk had been thrown from the vehicle and had life-threatening injuries.
He was airlifted to a Toronto trauma centre.
A 22-year-old woman was not seriously injured in the incident.
The section of road on County Road 46 is closed in both directions while investigators work.