South Lebanon is a city located in Union and Hamilton Townships in central Warren County in the southwestern part of the U.S. state of Ohio. The population was 6,384 at the 2020 census.

Union Township is one of the eleven townships of Warren County, Ohio, United States, located in the central part of the county. It was established January 3, 1815 and named Union as it was formed from parts of Deerfield and Turtlecreek Townships. The population was 6,251 as of the 2020 census.