Basin is an unincorporated community and census-designated place (CDP) in Jefferson County, Montana, United States. It lies about 10 miles (16 km) southeast of the Continental Divide in a high narrow canyon along Interstate 15 about halfway between Butte and Helena. Basin Creek flows roughly north to south through Basin and enters the Boulder River on the settlement's south side. The population was 212 at the 2010 census, down from 255 at the 2000 census.
Archaeologists have discovered evidence of human habitation from 10,000 years ago at a site near Clancy, 20 miles (32 km) northeast of Basin. From about 2000 BCE through the mid-19th century, nomadic tribes hunted bison in the grassy valleys that trend east, away from the Rocky Mountains and into the plains. By the time miners found gold in the streams in and near Basin, most of these tribes of Indians had been forced onto reservations by the U.S. government.
Basin rests above the Boulder Batholith, the host rock for many valuable mineral ores found in this part of Montana. After the town became a hub of gold and silver mining, Basin's population peaked at about 1,500 in the first decade of the 20th century but gradually declined as the mines were depleted. Abandoned mining equipment, closed or barricaded mine portals, and the ruins of a smelter and ore concentrator remain in Basin in the 21st century.
Historic buildings from Basin's heyday form much of the core of the CDP's small business district, which includes a fire station, a post office, two restaurants, a bar, a commercial gallery, and small specialty shops. Basin has a small elementary school, its own water system, and a low-power radio station. Local volunteers and elected trustees provide limited services to the settlement, but it relies on the government of Jefferson County, Montana, for law enforcement and other services. From 1993 through 2011 Basin was home to the Montana Artists Refuge.