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 (GNIS) lists 527 named islands in the state.
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.
Other islands of the San Francisco Bay Area:
The Farallon Islands are a group of rugged small islands over 20 miles (32 km) 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.
Suisun Bay is an arm of the San Francisco Bay estuary which connects the Sacramento and San Joaquin rivers to the Carquinez Strait.
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.
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. These Islands are part of the Greater Los Angeles Area.