Amaknak Island (Russian: Амакнак) or Umaknak Island (Aleut: Amaxnax̂; Russian: Умакнак) is the most populated island in the Aleutian Islands, an archipelago which is part of the U.S. state of Alaska.

Amaknak is an islet of the Fox Islands archipelago, a portion of the Aleutian Islands, in the Aleutians West Census Area of southwestern Alaska. Amaknak Island is located within Unalaska Bay, an inlet of the Bering Sea on the northeast side of Unalaska Island. At their closest point—the channel that leads from Unalaska Bay to Iliuliuk Harbor—the two islands are only about 200 feet (61 meters) apart. There is a 500-foot (152-meter) bridge joining the islands at another close point, where Iliuliuk Harbor connects with Captains Bay.

Amaknak's land area is 3.3 sq mi (8.5 km), which is dwarfed by its neighbor Unalaska Island, which has a land area of 1,051 sq. miles (2,722 km). The highest point on Amaknak is Mount Ballyhoo.

Despite its small size, Amaknak is the most populous of all the islands of the Aleutians chain, with 2,524 residents as of the 2000 census. Though located within the boundaries of the City of Unalaska, the inhabitants of Amaknak generally regard themselves as residents of Dutch Harbor, which is the portion of the City of Unalaska located on Amaknak Island. (The remaining 41% of Unalaska's residents live on Unalaska Island.)

• Battle of Dutch Harbor
• Dutch Harbor Naval Operating Base and Fort Mears, U.S. Army

• "The Battle Over Amaknak Bridge — Progress Versus Preservation in Alaska's Aleutian Islands", article in Archaeology : a Magazine Dealing with the Antiquity of the World no. 3: 28. 60, 2007, by Heather Pringle.

53°54′37″N 166°32′12″W / 53.91028°N 166.53667°W / 53.91028; -166.53667