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 Bay drains water from approximately 40 percent of California. Water from the Sacramento and San Joaquin rivers, and from the Sierra Nevada mountains, flow into Suisun Bay, which then travels through the Carquinez Strait to meet with the Napa River at the entrance to San Pablo Bay, which connects at its south end to San Francisco Bay. It then connects to the Pacific Ocean via the Golden Gate strait. However, this entire group of interconnected bays is often called the San Francisco Bay.
The bay covers somewhere between 1,000–4,000 km2, depending on which sub-bays (such as San Pablo Bay), estuaries, wetlands, and so on are included in the measurement. The main part of the bay measures 5–19 km wide east-to-west and somewhere between 77 km and 97 km north-to-south.
San Francisco Bay is the second-largest estuary on the Pacific coast of the Americas, following the Salish Sea in Washington State and British Columbia, Canada.
