The crashhappened at about 8:15 pm in Augusta just north of exit 109.
State Police say a car driven by 25-year-old Tara Gamwell of Portland crossed the median of the interstate, then rolled several times and collided with with a vehicle driven by 19-year-old Amanda Garwood of Winthrop.
Garwood died at the scene.
Gamwell suffered multiple injuries and is being treated at Central Maine Medical Center in Lewiston.
The Interstate was closed for more than two hours while troopers investigated.
No word yet on why Gamwell’s vehicle went out of control and into the other lane.