Marion County is a county located in the U.S. state of Mississippi. As of the 2020 census, the population was 24,441. Its county seat is Columbia. Marion County is named for American Revolutionary War guerrilla leader Francis Marion also known as The Swamp Fox.

Columbia is a U.S. city in and the county seat of Marion County, Mississippi, United States. Formed six years before Mississippi was admitted to statehood, Columbia was named for Columbia, South Carolina, from which many of the early settlers had migrated. The population was 5,864 as of the 2020 census, down from 6,582 in 2010.