Alluitsoq (Old Spelling: Agdluitsok) is the name of a former settlement in southern Greenland, located on the Alluitsoq or Lichtenau Fjord near Cape Farewell. It is about 7 kilometers from Ammassivik (Sletten), located on the opposite side of the same fjord.
It was founded as Lichtenau (German: «Light Water») by the Moravian missionary Gotfried Grillich and five families in 1774. For a time, it was the largest permanent settlement in Greenland. The mission was surrendered to the Lutheran Church of Denmark in 1900.
The site has a large graveyard and was used as a children's home for the Gertrud Rask Institute between 1942 and 1980. The fjord separates in two at the end. One houses the largest waterfall in Greenland, Qorlortorsuaq, and a trout farm. The other holds a Norse farm's ruins.