The San Francisco Bay Area, commonly known as the Bay Area, is a region of California based around the San Francisco Bay, including both the San Pablo Bay, and Suisun Bay estuaries, in Northern California. The Bay Area is defined by the Association of Bay Area Governments to include the nine counties that border the aforementioned estuaries: Alameda, Contra Costa, Marin, Napa, San Mateo, Santa Clara, Solano, Sonoma, and San Francisco. Other definitions may be either smaller or larger, and may include neighboring counties that do not border the bay such as Santa Cruz and San Benito ; or San Joaquin, Merced, and Stanislaus . The most populous cities of the Bay Area are Oakl San Francisco, and San Jose.