List of islands of California

This list of islands of California is organized into sections, generally arranged from north to south. The islands within each section are listed in alphabetical order.
The Geographic Names Information System lists 527 named islands in the state.

Humboldt County

Offshore

Humboldt Bay

All three islands in Humboldt Bay are located in the narrow midsection of the bay. This portion of the bay is located within the City of Eureka, California entirely within Humboldt County.

Island	Image	Coordinates	Description
Daby Island			The smallest of the three islands within Humboldt Bay, Daby Island has a maximum elevation of and is located slightly northeast of Woodley Island.
Tuluwat Island			The largest island, long, was originally the center of culture and population of the indigenous Wiyot people. Now protected, no public access is allowed, except for the Wiyot and grandfathered residents.
Woodley Island			The second largest of the three islands within Humboldt Bay contains: the Woodley Island Marina, the Eureka regional office of the National Weather Service, and offices of the Humboldt Bay Harbor Recreation & Conservation District.

San Francisco Bay Area

Island	Image	Coordinates	Counties	Description
Alameda Island			Alameda, San Francisco	This long island in San Francisco Bay is the main part of the City of Alameda.
Alcatraz Island			San Francisco	This island in San Francisco Bay once served as a lighthouse, a military fortification, a military prison, and as a federal prison until 1963. It is now part of the Golden Gate National Recreation Area.
Angel Island			Marin, San Francisco	With an area of, this island in San Francisco Bay processed approximately 1 million immigrants to the U.S. during 1910 to 1940. It is currently a state park.
Año Nuevo Island			San Mateo	Small Pacific island, about long, near Año Nuevo Point, south of the Golden Gate. It is protected by the Año Nuevo State Reserve as an important habitat for seabirds and other coastal wildlife.
Bair Island			San Mateo	This island in San Francisco Bay near Redwood City is part of the Don Edwards San Francisco Bay National Wildlife Refuge.
Bay Farm Island			Alameda	This former island in San Francisco Bay has been connected to the mainland. It is part of the City of Alameda.
Belvedere Island			Marin	This former island in Richardson Bay has been connected to the mainland. It is part of the City of Belvedere.
Bird Island			Marin	Small Pacific island between Point Bonita and Rodeo Cove.
Bird Rock			Marin	Small Pacific island west of Tomales Point, primarily a seabird colony. It covers.
Brewer Island			San Mateo	Coterminous with Foster City.
Brooks Island			Contra Costa	A island in San Francisco Bay south of Richmond, protected as part of the Brooks Island Regional Shoreline.
The Brothers			Contra Costa	Two small islands, East Brother and West Brother, located west of Point San Pablo. Each is about long. East Brother has a lighthouse and a bed and breakfast.
Castro Rocks			Contra Costa	Beneath the Richmond–San Rafael Bridge.
Coast Guard Island			Alameda	Located in the Oakland Estuary, this artificial island is part of the City of Alameda. It is home to various United States Coast Guard facilities.
Corinthian Island			Marin	This former island was joined to the mainland in the 1980s. It is split between the city of Belvedere and the town of Tiburon.
Dolphin Isle			San Mateo	Artificial island in Foster City Lagoon. Residential.
Greco Island			San Mateo	This island in San Francisco Bay near Redwood City is part of the Don Edwards San Francisco Bay National Wildlife Refuge.
Gull Rock			Marin	A Pacific island near Mount Tamalpais, about long.
Hog Island			Sonoma	Island in the Petaluma River wetlands.
Hog Island			Marin	A island in Tomales Bay.
Hooks Island			Santa Clara	tidal salt marsh island in the Palo Alto Baylands Nature Preserve
Kent Island			Marin	An island in Bolinas Lagoon, near the town of Bolinas. About long.
Mare Island			Solano	An island in San Pablo Bay near Vallejo. About long, site of a major shipyard.
East Marin Island			Marin	Near San Rafael, California. Pictured on the right in the image.
West Marin Island			Marin	Near San Rafael, California. Pictured on the left in the image.
Mussel Rock			San Mateo	A stack in the Pacific Ocean near Daly City. About long.
The Needles			Marin	Rock islets at Lime Point in Fort Baker near the Golden Gate Bridge's northern cable house.
Newby Island			Santa Clara	Near Alviso, San Jose.
Ogilvie Island			Santa Clara	Near Alviso, San Jose.
Rat Rock			Marin	An tall rock north of China Camp.
Red Rock Island			Contra Costa, Marin and San Francisco	This uninhabited island is located in San Francisco Bay just south of the Richmond–San Rafael Bridge, near the meeting point of three counties. It is privately owned.
San Pedro Rock			San Mateo	A Pacific island near the city of Pacifica. About long.
Seal Rocks			San Francisco	A series of large rocks in the Pacific Ocean that host a sea lion colony.
Seal Rock			San Mateo	A Pacific island south of Half Moon Bay, about long.
The Sisters			Marin	A pair of small islands in San Pablo Bay, south of Point Saint Pedro.
Treasure Island			San Francisco	This artificial island in San Francisco Bay is tied to Yerba Buena Island. It was dredged out of the bay to house the Golden Gate International Exposition of 1939-40.
Yerba Buena Island			San Francisco	This island in San Francisco Bay is home to a Coast Guard station. The San Francisco–Oakland Bay Bridge passes through it by means of a tunnel.

Farallon Islands

The Farallon Islands are a group of rugged small islands over offshore from the mainland of the City and County of San Francisco, which they are also formally within. They consist of over twenty small islets divided into north, south and middle sections, as well as a major bank, Fanny Shoal. The surrounding waters were once used as a disposal site for radioactive waste.

Island	Image	Coordinates	Description
Aulone Island and Great Arch Rock			North of Southeast Farallon Island, measuring wide and long.
Drunk Uncle Islets			Group of small islets north of Maintop Island.
Farallón Viscaíno
Middle Farallon Island			Medium-sized islet northwest of Southeast Farallon Island. It is long and has an area of.
North Farallon Island			Medium-sized islet long and high, covering.
Peñasco Quebrado
Piedra Guadalupe
Island of St. James			Medium-sized islet in size, measuring long and high.
Sea Lion Rock			Small islet northwest of Aulon Island, about long.
Seal Rock			Small islet south of Southeast Farallon Island, with a maximum height of.
Maintop Island			West of Southeast Farallon Island, and has a maximum height of.
Southeast Farallon Island			Is the largest of the Farallons, covering. It is the only inhabited Farallon Island, and is also the site of Farallon Island Light.
Sugarloaf Island			Directly to the northeast of Aulone and Great Arch Rock, about high.

Suisun Bay

is an arm of the San Francisco Bay estuary which connects the Sacramento and San Joaquin Rivers to the Carquinez Strait.

Island	Image	Coordinates	County	Description
Chipps Island			Solano
Dutton Island			Solano
Freeman Island			Solano	Small island, second from top on left hand of frame.
Grizzly Island			Solano
Hammond Island			Solano
Joice Island			Solano	A marshy island long, north of Grizzly Bay.
Morrow Island			Solano	A small island that has an elevation of 2 meters- 7 feet.
Point Buckler Island			Solano	A private marshy island of, with some history as a kiteboarding destination.
Roe Island			Solano	In Suisun Bay. On far right of picture.
Ryer Island			Solano	island, between Suisun Bay and Suisun Cutoff. About long. Largest island in the photo.
Seal Islands			Contra Costa	In Suisun Bay.
Simmons Island			Solano
Snag Island			Solano	Smallest island in the photo, top center.
Van Sickle Island			Solano	An island long at the junction of the Sacramento River, San Joaquin River, and Suisun Bay.
Wheeler Island			Solano