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