Lebanon is a home rule-class city and the county seat of Marion County, Kentucky, in the United States. The population was 6,274 at the 202…Lebanon is a home rule-class city and the county seat of Marion County, Kentucky, in the United States. The population was 6,274 at the 2020 census, up from 5,539 in 2010. Lebanon is located in central Kentucky, 63 miles southeast of Louisville. A national cemetery is nearby.