Calhoun County is a county in the U.S. state of South Carolina. As of the 2020 census, its population was 14,119, making it the third-least populous county in the state. Its county seat is St. Matthews. In terms of land area, it is also the smallest county in the state.

St. Matthews is a town in Calhoun County, South Carolina, United States. The population was 2,021 at the 2010 census, a decline from 2,107 in 2000. It is the county seat of Calhoun County.