The Dearborn River is a tributary of the Missouri River, approximately 70 mi (113 km) long, in central Montana in the United States.

It flows generally southeast through secluded canyons, and joins the Missouri near Craig.

It is crossed by the Dearborn River High Bridge, which was constructed in 1897.

It is a popular destination for whitewater rafting and fly fishing.

Whirling disease has become a significant problem among trout in the river.