Fairfield County is a county located in the U.S. state of South Carolina. As of the 2020 census, its population was 20,948. Its county seat is Winnsboro.

Winnsboro is a town in Fairfield County, South Carolina, United States. The population was 3,550 at the 2010 census. The population was 3,215 at the 2020 census, a population decrease of approximately 9.5% for the same 10 year period. It is the county seat of Fairfield County. Winnsboro is part of the Columbia, South Carolina metropolitan Area as well as a suburb of Columbia.