A young man is fighting for his life after a hit-and-run collision in Melbourne's north-west. 

The man was jaywalking at a crossing on Racecourse Road, Flemington, about 12.30am on Saturday when he was hit by a car, a police spokeswoman said.

The driver failed to stop at the scene but was arrested in a nearby carpark and taken to hospital under police guard.

The 36-year-old Meadow Heights man was later released pending summons, police said. 

Ambulance Victoria spokesman Ray Rowe said the pedestrian, aged in his late teens, was taken to the Royal Melbourne Hospital in a critical condition with injuries to his upper body.

Police have asked that anyone who witnessed the collision to call Crime Stoppers on 1800 333 000 or visit www.crimestoppersvic.gov.au