Kathleen Brown, 23, of Billings, has been identified by the Yellowstone County Coroner's office as the woman who died in a rollover early Saturday.
The crash happened on Rimrock Road, just east of 62nd Street West.
Brown died when her Chevy Nova left the road and rolled into the ditch.
Lt. Kevin Iffland said that the Billings Police Department is still investigating the incident. It was initially thought that the woman may have drifted north on the road and overcorrected, causing the car to roll at least once.
The woman was not wearing a seat belt and was found dead in the car.
A call to Billings Police came at 4:21 a.m. Saturday when a caller saw the car in the ditch. It is not known how long the car was there.