Unalaska () is an island in the Fox Islands group of the Aleutian Islands in the US state of Alaska located at . The island has a land area of . It measures long and wide. The city of Unalaska, Alaska, covers part of the island and all of neighboring Amaknak Island where the Port of Dutch Harbor is located. The population of the island excluding Amaknak as of the 2000 census was 1,759 residents.

Unalaska (Aleut: Iluulux^) is a city in the Aleutians West Census Area, a regional component of the Unorganized Borough in the U.S. state of Alaska. Unalaska is located on Unalaska Island and neighboring Amaknak Island in the Aleutian Islands off mainland Alaska. The population was 4,376 at the 2010 census, which is 79% of the entire Aleutians West Census Area. Unalaska is the second-largest city in the Unorganized Borough, behind Bethel.