Police and emergency services responded to reports of a single vehicle crash in Ravenhall last night.
Investigators have been told a Toyota sedan was travelling west bound on the Western Highway abut 8.15pm.
Witnesses say they saw the car swerve into the emergency lane before crashing into the retaining wall.
The driver, a 17-year-old boy from St Albans who was the sole occupant of the vehicle, was taken to hospital with life-threatening injuries.
Anyone who witnessed the vehicle travelling on the Western Highway prior to the crash or with dashcam footage is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au