A male pedestrian has been flown to hospital in a critical condition after he was hit by a car in Sydney's west.

Emergency services were called to Marion Street, Bankstown, about 7.20pm to reports a 31-year-old man had been hit by a car.

Three ambulance crews and a helicopter attended the scene, and paramedics intubated the man before he was flown by helicopter to Liverpool Hospital.

A police spokeswoman said the crash is being investigated and the driver of the car has been taken for mandatory blood and urine testing.

More to come.