The 56-year-old man was driving a Harley Davidson motorcycle southbound on U.S. 93 when the road curved to the left and the bike went off the right side of the road.
The driver lost control and was thrown as the motorcycle overturned in the ditch. He was not wearing a helmet and was pronounced dead at the scene.
The crash marks the 118th fatality on Montana roads and joins three other crashes that resulted in fatalities on Monday.
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