San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, San Jose, and Oakland.

San Francisco, officially the City and County of San Francisco, is a commercial, financial, and cultural center in Northern California. With a population of 808,437 residents as of 2022, San Francisco is the fourth most populous city in the U.S. state of California. The city covers a land area of 46.9 square miles at the end of the San Francisco Peninsula, making it the second-most densely populated large U.S. city after New York City and the fifth-most densely populated U.S. county, behind only four New York City boroughs. Among the 92 U.S. cities proper with over 250,000 residents, San Francisco is ranked first by per capita income and sixth by aggregate income as of 2022.