Fallon is an unincorporated small town in Prairie County, Montana, United States.

[4] According to the United States Census Bureau, the CDP has a total area of 5.1 square miles (13 km2), all land.

The racial makeup of the CDP was 98.55% White, 0.72% Native American, and 0.72% from two or more races.

31.7% of all households were made up of individuals, and 14.3% had someone living alone who was 65 years of age or older.

There were 26.2% of families and 35.8% of the population living below the poverty line, including 68.4% of under eighteens and 22.7% of those over 64.