[1] Ammassalik Island is located in the King Christian IX Land region.

Separating Ammassalik Island from the mainland of Greenland are the wide Sermilik Fjord in the west and the Ikaasartivaq Strait in the northeast.

The highest point of the island is a glaciated peak in the northern part, at 1,352 m (4,435.7 ft).

[2] The only permanently inhabited settlement on the island is Tasiilaq town on the south coast of the island, with 1,893 inhabitants as of 2009[update],[3] the most populous community on the eastern coast, and the seventh-largest town in Greenland.

The research station Sermilik is located 15 km northwest of Tasiilaq on the west coast.