NSW woman critical after being hit by car

A 24-year-old woman is in a critical condition after being hit by a car in western Sydney.

A green Toyota hit the pedestrian on Showground Road at Sydney Olympic Park early on Saturday morning.

The woman was taken to Westmead Hospital where she remains in a critical condition.

The 20-year-old male driver of the car wasn't hurt in the crash and has been assisting police. He's been since released.

Police are calling for witnesses that may have been in the area to come forward, particularly a taxi which was in the area.