The Boulder River is a tributary of the Jefferson River, approximately 71 mi (114 km) long, in southwestern Montana in the United States.

It rises in the Rocky Mountains at the continental divide in the Deerlodge National Forest in western Jefferson County. It flows east and southeast through the mountains past Boulder, then south to join the Jefferson near Cardwell.

The river is a popular destination for fly fishing.

See also

• List of Montana rivers

External links

• Southwestern Montana relief map
• Boulder River Pictures & Information

Rivers of Montana