Pituffik is a former settlement in northern Greenland, located at the eastern end of Bylot Sound by a tombolo known as Uummannaq, near the current site of the American Pituffik Space Base, formerly Thule Air Base. The former inhabitants were relocated to the present-day town of Qaanaaq. The relocation and the fallout from the 1968 Thule Air Base B-52 crash in the vicinity are a contentious issue in Greenland's relations with Denmark and the United States.

A tombolo is a sandy or shingle isthmus. A tombolo, from the Italian tombolo, meaning 'pillow' or 'cushion', and sometimes translated incorrectly as ayre, is a deposition landform by which an island becomes attached to the mainland by a narrow piece of land such as a spit or bar. Once attached, the island is then known as a tied island.