Located in the southern part of Melville Bay, Kiatassuaq Island has an elongated shape, with an east-west orientation. The name of the island means "a large torso" in the Greenlandic language. Kullorsuaq is the closest settlement to Kiatassuaq Island.
There is a number of smaller mountain lakes on the island, and one larger Tasersuaq Lake at the lower, eastern end of the island. The island is very mountainous, with a glaciated ridge spanning its entire length. The highest point on the island is an unnamed peak of 940 m (3,080 ft) in the center of the island.
Several other summits of the island ridge exceed 700 m (2,300 ft), from the massif overlooking Tasersuaq Lake in the east to the bastion over the Wilcox Head promontory in the west.