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

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 (Petaluma River)			Sonoma	Island in the Petaluma River wetlands.
Hog Island (Tomales Bay)			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, California)			San Francisco	A series of large rocks in the Pacific Ocean that host a sea lion colony.
Seal Rock (San Mateo County, California)			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

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

Sacramento–San Joaquin River Delta

The Sacramento–San Joaquin River Delta is an inverted delta at the juncture of the Sacramento and San Joaquin rivers. There are about 57 named islands in the Delta.

Island	Image	Coordinates	County	Description
Andrus Island			Sacramento	island, bounded by Sacramento River, Georgiana Slough, Mokelumne River, San Joaquin River, Jackson Slough, and Seven Mile Slough.
Bacon Island			San Joaquin	island, bounded by Connection Slough, Old River, Woodward Island, and Middle River
Bethel Island			Contra Costa	island, bounded by Taylor Slough, Piper Slough, Sand Mound Slough, and Dutch Slough
Bishop Tract
Brack Tract
Byron Tract
Bouldin Island			San Joaquin	island bounded by South Mokelumne River, Little Potato Slough, Potato Slough, and Mokelumne River.
Bradford Island			Contra Costa	island in the lower delta bounded by the San Joaquin River, False River and the Bradford Island canal/slough. Accessible only by Ferry via Jersey Island, just south of it.
Browns Island			Contra Costa	island, bounded by Middle Slough, New York Slough, and Suisun Bay. On the left in photo.
Canal Ranch Tract
Coney Island			Contra Costa
Dead Horse Island			Sacramento
Decker Island			Solano	Small island on the top-left in photo.
Empire Tract
Fabian Tract
Fay Island			San Joaquin
Glanville Tract
Grand Island			Sacramento
Hastings Tract
Holland Tract
Hotchkiss Tract
Jersey Island			Contra Costa	island, bounded by False River, Piper Slough, Taylor Slough, Dutch Slough and San Joaquin River.
Jones Tract		upper: lower:	San Joaquin	island, bounded by Empire Cut, Whiskey Slough, Trapper Slough, and Middle River, 10 km east of Stockton
King Island			San Joaquin	island bounded by White Slough, Bishop Cut, Disappointment Slough, and Honker Cut
Kings Island			Contra Costa	island in Old River
Little Mandeville Island			San Joaquin
Little Tinsley Island
Mandeville Island			San Joaquin
McDonald Island			San Joaquin	island, bounded by San Joaquin River, Middle River, Latham Slough, and Empire Cut.
Medford Island			San Joaquin
Merritt Island			Yolo	A island formed by the Sacramento River to the southeast and Elk Slough to the west, located directly across the Sacramento from Hood.
Mildred Island			San Joaquin
Netherlands Island
Neville Island
New Hope Tract
Orwood Tract
Palm Tract
Pierson District
Prospect Island			Solano
Quimby Island			Contra Costa
Rhode Island			Contra Costa
Rindge Tract
Rio Blanco Tract
Roberts Island			San Joaquin
Ruff and Ready Island			San Joaquin River	An approximately 2.3-square-mile island in Stockton, California. A United States Navy installation built there during World War II was phased out in 1995 and later transferred to the Port of Stockton.
Ryer Island			Solano	, bounded by Miner Slough and Steamboat Slough.
Sargent Barhart Tract
Sherman Island			Sacramento	island bounded by the Sacramento River, Three Mile Slough, and the San Joaquin River.
Shima Tract
Shin Kee Tract
Staten Island			San Joaquin	island bounded and flanked by the North Mokelumne River and South Mokelumne River.
Stewart Tract
Sutter Island			Sacramento	Formed by Sacramento River to the northeast, Steamboat Slough to the southeast, and Sutter Slough to the west. Located across the Sacramento River from Paintersville.
Sycamore Island
Terminous Tract
Twitchell Island			Sacramento	, bounded by Seven Mile Slough, San Joaquin River, and Three Mile Slough
Tyler Island			Sacramento
Union Island			San Joaquin
Van Sickle Island			Solano
Veale Tract
Venice Island			San Joaquin	island bounded by Potato Slough, Little Connection Slough, Stockton Deepwater Channel Venice Cut, and San Joaquin River.
Victoria Island			San Joaquin	island bounded by North Victoria Canal, Middle River, Victoria Canal, and Old River.
Webb Tract
West Island			Sacramento
Winter Island			Contra Costa	On the right in photo.
Woodward Island			San Joaquin	island bounded by Bacon Island, Old River, Middle River, and Woodward Canal
Wright-Elmwood Tract

Channel Islands

The Channel Islands are a group of eight main islands and several minor islands in the Pacific Ocean off the coast of Santa Barbara, Los Angeles, and Ventura counties in Southern California. The four northern islands are protected in Channel Islands National Park, while two are used by the U.S. Navy.

Island	Image	Coordinates	Description
Anacapa Island			Located off the coast of Ventura, California. It contains of land spread across three mountainous islets. The island has only three permanent residents. Part of the Greater Los Angeles Area.
Begg Rock			A high rock, located from San Nicolas Island.
Prince Island			Located near San Miguel Island and measures about.
San Clemente Island			Southernmost Channel Island, containing of land. It is long. An active U.S. Navy base is located on the island. In Los Angeles County.
San Juan Island			Historical San Juan Island, modern Cortes Bank, is a high seamount, an island submerged 6 feet and more, 96 mi SW of San Pedro, 111 mi W of Pt Loma, and 47 mi SW of San Clemente Island. The outermost feature in the Channel Islands, it has been visible as an island from elevations on San Clemente Island on clear days, and known for some of the world’s largest surf. Offshore from Orange County.
San Miguel Island			Westernmost Channel Island, measuring long, wide, and containing of land. The island is uninhabited, and is rarely visited. Part of the Greater Los Angeles Area.
San Nicolas Island			Is said to be the most remote island of the Channel Islands, and is used by the U.S. Navy as a weapons testing and training facility. It has no civilian inhabitants, but is inhabited by military personnel. It covers. Part of the Greater Los Angeles Area.
Santa Barbara Island			Smallest Channel Island at in area; it is located roughly between San Nicolas and Santa Catalina Islands. Part of the Greater Los Angeles Area.
Santa Catalina Island			The most populous of the Channel Islands, with 3,696 residents as of 2000. It is about long with a maximum width of. It covers. In Los Angeles County.
Santa Cruz Island			Santa Cruz Island measures long with an average width of, covering. It is the largest Channel Island. The island is now on public land, but was previously the largest privately owned island of the continental United States. Part of the Greater Los Angeles Area.
Santa Rosa Island			Santa Rosa Island occupies, and is the second largest Channel Island. The island has a permanent population of 2 persons, and is about off the coast of Santa Barbara, California. Part of the Greater Los Angeles area.
Shag Rock			Small islet located off the north shore of Santa Barbara Island, and is only about.
Sutil Island			Located off the southwest shore of Santa Barbara Island, and is about. It is named for a Spanish ship exploring the West Coast in an expedition led by Sebastián Vizcaíno.

Newport Bay

The bay associated with Newport Harbor and the city of Newport Beach, California.

Island	Image	Coordinates	Description
Balboa Island			A, densely populated harbor island with 1,500 expensive homes. Partially created as a result of the Santa Ana River flooding in 1824, then artificially expanded to its present size.
Bay Island			West of Balboa Island.
Collins Island			A small island located at the end of Balboa Island
Harbor Island
Lido Isle			Northwest of Balboa Island.
Linda Isle
Newport Island			Located at the far west end of the bay