Tasiilaq is a town situated on Ammassalik Island in southeastern Greenland, within the municipality of Sermersooq. It lies on the shore of a natural harbour in Tasiilaq Fjord, which is an inlet of the larger Ammassalik Fjord emptying into the North Atlantic. The settlement is located approximately 106 kilometers south of the Arctic Circle, positioned near the Sermilik Fjord to the west.

The permanent settlement was founded in 1894 as a Danish trading station by Danish explorers who initially named it Ammassalik. The area had been deserted for two hundred years prior due to back migrations to the western coast, with the region not being settled again until the late eighteenth century. The official name changed to Tasiilaq in 1997, meaning the place at the lakes, though locals had long used this term.

The town features a mix of administrative buildings, hotels, and a hospital, set against a backdrop of high mountains. Notable landmarks include the Sermilik Station for glacier research and two churches, the second built in 1986 with interior decoration by artist Aka Høegh. The landscape is defined by its natural harbour and proximity to the Mittivakkat Glacier, offering dramatic views of icebergs and fjords.

Tasiilaq serves as the main location where East Greenlandic is spoken and attracts visitors seeking outdoor activities such as ice climbing, glacier hikes, and kayaking. The local economy has shifted from hunting to cod fisheries, while tourism offers boat trips and whale watching. The community maintains traditions of fishing and hunting, with residents often living by administration and service roles.

With 1,985 inhabitants as of 2020, Tasiilaq is the most populous community on the eastern coast and one of Greenland's fastest-growing towns. Access is primarily via helicopter or boat, as there are no roads far outside the town. The climate is tundra, characterized by long, cold winters and short, cool summers, with occasional severe weather events like piteraqs.