Large, nearly landlocked bay indenting west-central California, U.S. A drowned river valley paralleling the coastline, it is connected with the Pacific Ocean by the Golden Gate Strait, which is spanned by the Golden Gate Bridge .
The bay is one of the world's finest natural harbours. Treasure, Yerba Buena, Angel, and Alcatraz islands are there; the cities of San Francisco , Oakland , and Berkeley are nearby.