Sourdough is an unincorporated community and ghost town in Sweet Grass County, Montana, United States.

Sourdough appears on the Ryan Creek U.S. Geological Survey Map.

Established in 1912, Sourdough was an isolated village situated in the Crazy Mountains.

The schoolhouse has been restored and relocated to Big Timber and part of the Crazy Mountain Museum.

This Sweet Grass County, Montana state location article is a stub.