Major Crash officers are investigating a fatal crash that occurred in Coolup on Friday night.
At about 8.40pm, a grey Nissan Patrol was heading north along the South Western Highway when the driver lost control of the vehicle.
The car left the road and struck a tree.
A 31-year-old woman, who was in the front passenger seat, received critical injuries and died at the scene.
The 34-year-old male driver of the vehicle received serious injuries and was airlifted to Royal Perth Hospital.
Police would like to speak to anyone who saw the crash, the Nissan Patrol travelling in the area prior or who was in the vicinity around the time with dash-cam vision.
Anyone with any information relating to the crash is asked to call Crime Stoppers on 1800 333 000 or report online at www.crimestopperswa.com.au.