The 37-year-old woman and 42-year-old man were pronounced dead at the scene.
A further two people are in a critical condition and a third has been described as "serious".
The crash, which involved a silver Mercedes car and a white Vauxhall van, happened on the eastbound carriageway between Polmont and Linlithgow at about 21:00 on Friday.
Anyone who witnessed the crash is asked to contact police.
A Police Scotland spokeswoman said: "This has been a serious road traffic collision.
"We are keen to hear from anyone who witnessed it or who has information that can assist us in our inquiries."
A nine-year-old girl has died, along with a man and woman, in a crash on the M9 in West Lothian.