Esther Island is an island in the northwestern part of Prince William Sound of the Gulf of Alaska in the state of Alaska, USA. It has a land area of 127.336 km² (49.165 sq mi) and a resident population of 31 persons as of the 2000 census. The island is the site of the South Esther Island State Marine Park, one of the Alaska State Parks system. The island includes no permanent settlements other than the Wally Noerenberg Hatchery, one of the World's largest Salmon hatcheries, owned and operated by the Prince William Sound Aquaculture Corporation (PWSAC). The hatchery raises three different species of salmon Pink salmon, Chum salmon, and Coho salmon. The hatchery is located within the State Marine Park. The island is only accessible by floatplane or boat.