Police in West Lothian are appealing for witnesses to the fatal collision, which happened about 10.45pm yesterday.
A blue Ford Mondeo travelling east left the road about one mile before junction 2 on the motorway.
The car came to a stop in a field.
The 37-year-old female driver suffered fatal injuries and was pronounced dead at the scene.
Road policing officers attended along with other emergency services.
The road was closed for about six-and-a-half hours while inquiries were carried out at the scene.
Officers have appealed for anyone who can help to come forward.
Constable Phil Dickson, from Dalkeith’s Road Policing Unit, said: “Sadly this collision has resulted in a woman losing her life and our thoughts are with her family and friends at this difficult time.
“We’re eager to establish the full circumstances of this collision and I would appeal to any drivers using the M8 motorway last night and who saw the vehicle immediately prior to the incident, or who witnessed what happened, to contact us as soon as possible.”
Those with information can contact Police Scotland via 101 or to Crimestoppers on 0800 555 111.
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