Lebanon is a city in St. Clair County, Illinois, United States.

The population was 4,691 at the 2020 census It is a part of the Metro East region of the Greater St. Louis metropolitan area.

Lebanon is home to McKendree University, the oldest college in Illinois.

There were 1,389 housing units at an average density of 647.2 per square mile (249.9/km2).

28.5% of all households were made up of individuals, and 12.9% had someone living alone who was 65 years of age or older.