San Francisco, officially known as the City and County of San Francisco, is a city located in the United States. It serves as the fourth-most populous city in California and ranks as the 17th-most populous city in the United States, with a population of 826,079 as of 2025.
The city is characterized by high economic indicators; as of 2024, it ranked first in per capita income among U.S. cities with populations over 200,000 and sixth in aggregate income. It also ranks third in population density within that same category. The surrounding metropolitan statistical area houses approximately 4.6 million residents, while the broader San Jose–San Francisco–Oakland combined statistical area is the fifth-largest in the United States with roughly 9.2 million residents.