Police are appealing for witnesses following a collision in Thomastown last night (21 January), Victoria Police say.
Emergency services responded to the collision at the intersection of High Street and Newton Street just before 11pm.
It is believed a motorcyclist was travelling north when it was struck by a dark coloured Ford sedan which was attempting to turn into Newton Street.
The driver of the Ford and sole occupant, a 72-year-old Thomastown man stopped and rendered assistance.
He was taken to hospital for observation.
The motorcyclist was not wearing a helmet at the time of the collision and he was taken to hospital with life threatening injuries.
The exact cause of the collision is yet to be determined and the investigation remains ongoing.
Police are appealing for anyone who may witnessed the motorbike travelling on High Street prior to the collision or who have dash cam footage to contact Crime Stoppers.