Four-year-old killed after being hit by car in Sydney's west

A four-year-old boy has died after being hit by a car in Sydney's west.

The boy was struck by a Ford sedan on Glossop Street in North St Marys, about 45km west of the CBD, around midday today.

While emergency services provided treatment to the boy, he died while on the way to hospital.

READ MORE: Millions set to be hit by scorching conditions on New Year's Eve

"The boy was treated by NSW Ambulance paramedics, however, he died a short time later en route to hospital," NSW Police said.

"The male driver was taken to Nepean Hospital for mandatory testing.

"A crime scene has been established and police have commenced an investigation into the incident."

Anyone with information about the incident, including dashcam footage, has been urged to contact authorities.