The 18-year-old man was taken to Aberdeen Royal Infirmary following the incident on the A93 on the outskirts of Aberdeen. A 27-year-old man was also taken to hospital with serious injuries, while a 19-year-old was treated for minor wounds.
The incident involving the grey Audi A6 happened at 12.40am today. The road was closed for investigations and until repairs to the road surface can be made.
Sergeant Chris Smith said: "It is important we establish exactly what happened at the time of the crash and in the moments leading up to it.
"If you witnessed the crash and have yet to speak to officers, please get in touch. If you were driving in the area before 12.40am and saw a car matching this description, please also come forward.
"We would like to speak to anyone who has dashcam or CCTV footage which assist with our investigation."