one of several smaller groups of islands within the Aleutian Islands, southwestern Alaska, U.S. They lie between the Pacific Ocean (south) and the Bering Sea (Bering Sea and Strait) (north) and extend east-west for about 270 miles (430 km) east of Rat Islands. The largest islands in the group are Adak, Amlia, Atka, Kanaga, and Tanaga. The Andreanof Islands were strategically important in World War II; Adak (formerly Adak Station) was used as a staging point to win back the Japanese-held islands of Attu and Kiska. In March 1957 the Andreanofs were the site of the third largest earthquake in the 20th century, which set off a Pacific-wide tsunami.

Adak, the largest settlement in the island group, formerly housed extensive U.S. naval facilities. The base was closed in 1997, however, and the city's population declined dramatically from a peak of some 6,000 to just several hundred; it is now populated largely by native Aleuts. The islands are part of the extensive Alaska Maritime National Wildlife Refuge.