Seneca is a city in Oconee County, South Carolina, United States. As of the 2020 census, Seneca had a population of 8,850. It is the principal city of the Seneca Micropolitan Statistical Area, which includes all of Oconee County, and is part of the greater Greenville-Spartanburg-Anderson, South Carolina Combined Statistical Area. Seneca was named for the nearby Cherokee town of Isunigu, which English colonists knew as "Seneca Town".