Fairmont is an unincorporated community and census-designated place (CDP) in Will County, Illinois, United States.

[5] According to the United States Census Bureau, the CDP has a total area of 1.6 square miles (4.1 km2), all land.

There were 901 housing units at an average density of 546.9 per square mile (211.2/km2).

21.8% of all households were made up of individuals, and 7.2% had someone living alone who was 65 years of age or older.

Pace provides bus service on Routes 509 and 834 connecting Fairmont to downtown Joliet and other destinations.