Coffeen is a small city in Montgomery County, Illinois, United States.

[4] Coffeen is in southeastern Montgomery County, along Illinois Route 185 (Main Street).

According to the U.S. Census Bureau, Coffeen has a total area of 1.16 square miles (3.00 km2), all land.

The racial makeup of the city was 98.87% White, 0.28% Native American, 0.56% Asian, and 0.28% from two or more races.

28.1% of all households were made up of individuals, and 18.5% had someone living alone who was 65 years of age or older.