A woman has died and three people are in hospital with serious injuries after a car rollover 30km south-west of the Gascoyne town of Mount Magnet.

The rollover happened on the Geraldton-Mount Magnet Road about 6am on Friday morning, with a man and three women in the car at the time, police spokeswoman Susan Usher said.

A woman died at the scene of the crash, while a man and two women were taken to Mount Magnet Hospital with serious but non life-threatening injuries.

Ms Usher said the Royal Flying Doctor Service would transport the injured trio to Royal Perth Hospital later today.