Lake Langisjór is a large lake southwest of Vatnajökull. It is 27 km², 20 km long and 2 km wide where it is widest. The height above sea level is 662 m. To the east of Langasjór lies a mountain range called Fögrufjöll, from which many cliffs lead into the lake and into them the fjords and bays cut. There is good char fishing in Langasjór. There is a fishing cabin at the western end of the lake.