The U.S. state of South Carolina is made up of 46 counties, the maximum allowable by state law.^[1] They range in size from 392 square miles (1,015 square kilometers) in the case of Calhoun County to 1,358 square miles (3,517 square kilometers) in the case of Charleston County. The least populous county is Allendale County, with only 7,369 residents, while the most populous county is Greenville County, with a population of 558,036, despite the state's most populous city, Charleston, being located in Charleston County.

In the colonial period, the land around the coast was divided into parishes corresponding to the parishes of the Church of England. There were also several counties that had judicial and electoral functions. As people settled the backcountry, judicial districts and additional counties were formed. This structure continued and grew after the Revolutionary War. In 1800, all counties were renamed as districts. In 1868, the districts were converted back to counties.^[2] The South Carolina Department of Archives and History has maps that show the boundaries of counties, districts, and parishes starting in 1682.^[3]

Historically, county government in South Carolina has been fairly weak.^[4] The 1895 Constitution made no provision for local government, effectively reducing counties to creatures of the state. Each county's delegation to the General Assembly, comprising one senator and at least one representative, also doubled as its county council. Under this system, the state senator from each county wielded the most power.^[5] From the eighteenth century to 1973, counties in South Carolina performed limited functions such as the provision of law enforcement and the construction of transportation infrastructure.^[4]

In 1964, the United States Supreme Court case Reynolds v. Sims required reapportionment according to the principle of "one man, one vote", which resulted in legislative districts crossing county lines. However, it was not until 1973 that the constitution was amended to provide for limited home rule at the county level.^[6] This was finally enacted in 1975 with the Home Rule Act,^[5] which provided for elected councils in each county. Further, in 1989, all counties were given the authority to exercise broad police powers.^[7] Thus, they may enact regulations and ordinances related to the provision or preservation of security, health, peace, and order, so long as the regulation is not inconsistent with state law.^[8] Nonetheless, all counties and municipalities in South Carolina lack “fiscal home rule,” meaning they may only enact taxes authorized by the General Assembly.^[5]

County ordinances become applicable within municipal boundaries when the municipality and the county make a formal agreement, and the municipality formally adopts the ordinance.^[9] Unincorporated areas are governed by the county's land use plans.^[10]

• Birch County, proposed in 2013 (portions of Lexington and Richland counties)

• List of municipalities in South Carolina
• List of census-designated places in South Carolina
• List of ghost towns in South Carolina
• List of former United States counties