Police are searching for a driver who mowed down a cyclist before fleeing on the Bellarine Peninsula.

The 48-year-old cyclist in hi-vis clothing was riding north on Princess Street in Drysdale at about 5.30pm on Thursday.

A vehicle has come up behind him near the railway line and Andersons Road, knocking him off his bike.

The driver, thought to be in a Toyota Hilux Ute did not stop.

A witness tried to go after the Ute but instead went back to help the cyclist who was lying on the road with head injuries.

The rider was taken to the Geelong hospital in a stable condition.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.