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.

Greenup County is a county located along the Ohio River in the northeastern part of the U.S. state of Kentucky. As of the 2020 census, the population was 35,962. The county was founded in 1803 and named in honor of Christopher Greenup. Its county seat is Greenup. Greenup County is part of the Huntington-Ashland, WV-KY-OH Metropolitan Statistical Area.