South San Francisco, California

South San Francisco is a city in San Mateo County, California, United States, on the San Francisco Peninsula in the San Francisco Bay Area. It is colloquially termed South City. The population was 66,105 as of the 2020 census, and was estimated at 64,941 in 2025. It is a separate municipality from the city of San Francisco to its north, and the lead of its source article gives only its county, its place on the peninsula, its nickname and its population counts, so this entry records those facts and leaves history, economy and landmarks to later depth work.