The 68-year-old woman driver is a critical condition after her car appeared to lose control heading on the slip road from the M73 at junction 8 of the M8.
Police said the silver Ford Fiesta was heading north when it seemed to lose control, leave the road and crash into a ditch on the verge around 3.30pm on Saturday.
The emergency services attended but the elderly woman was declared dead at the scene.
The driver is being treated at the Queen Elizabeth University Hospital in Glasgow.
Police closed the road as investigations were carried out and are now appealing for witnesses.
Motorists in the area at the time are also being asked to check their dash cam footage.