About 10.10pm on Saturday, emergency services were called to the Mid Western Highway about 5 kilometres north of Cowra, following reports of a crash.

According to initial investigations, a Toyota four-wheel-drive was travelling north on the highway when it left the roadway and crashed into a tree.

The driver, a woman believed to be in her 60s, died at the scene.

The passenger, a man also believed to be in his 60s, was treated at the scene by NSW Ambulance paramedics before being taken to Orange Health Service with serious injuries.

A crime scene was established and the southbound lane of the Mid Western Highway was closed as investigations took place.

Canobolas Local Area Command Inspector Peter Atkins said the deceased woman had yet to be formally identified.

A report will be prepared for the coroner.