Qassiarsuk is a settlement in the Kujalleq municipality, in southern Greenland. Its population was 89 in 2010.

Brattahlid was the site of the Erik the Red's estate in the times of the Norse Eastern Settlement. The current village is located in the same place.

The settlement is located roughly 5 km (3.1 mi) west of Narsarsuaq, on Narsaq Peninsula, on the northwestern shore of Tunulliarfik Fjord. The plains are wider than those of Narsaq at the far end of the peninsula, while the earth is also fertile, both factors contributing to farming and land cultivation being the primary occupation of the inhabitants.

It is possible to cross overland to Narsarsuaq, although crossing the glacial Narsarsuaq river is difficult due to deposits of silt quicksand the river carries from the Greenland ice sheet. All transport at Qassiarsuk is by sea, with boats linking the settlement to Narsarsuaq, home to the only international airport in southern Greenland. The airport primarily functions as a transfer point for passengers heading for the helicopter hubs of Air Greenland in Qaqortoq and Nanortalik.

Information based on