Flatwoods is a home rule-class city in Greenup County, Kentucky, United States. The population was 7,325 at the 2020 census, making it the largest city in Greenup County. Flatwoods is a part of the Huntington–Ashland metropolitan area. Locally, Flatwoods is considered to be a bedroom community, as it has no large employer within the city. Many residents work for CSX Transportation, Marathon Petroleum, or King's Daughters Medical Center.