Police were notified of the incident just before midnight last night.
The driver was ejected from the vehicle, which had landed in a paddock.
Police and members of the public located the injured man, who was taken to Nelson Hospital before being transferred by helicopter to Wellington Hospital’s ICU.
A search of the area where the vehicle came to a halt was conducted with the assistance of the Fire Service, which used thermal imaging equipment to ensure no-one else had been ejected from the car.
Senior Sergeant Clare Robertson, District Shift Commander, says Police do not believe there was anyone else in the car.
The Serious Crash Unit attended the scene of the crash overnight and its investigation continues.
Police are not seeking anybody else in relation to the incident.
Police Media Centre