| Langisjór | |
| Coords: | 64.1833°N -33°W |
| Basin Countries: | Iceland |
| Length: | 20km (10miles) |
| Width: | 2km (01miles) |
| Area: | 26km2 |
| Max-Depth: | 75m (246feet) |
| Elevation: | 670m (2,200feet) |
| Pushpin Map: | Iceland |
| Pushpin Map Alt: | Location of Langisjór in Iceland. |
Langisjór (pronounced as /is/) is a lake in the western part of Vatnajökull National Park, Iceland. It is around 20 km in length and up to 2 km wide, with a total surface area of about 26km2 and a depth of 75m at its deepest point.
The lake is situated rather far from civilisation at the south-western border of Vatnajökull at an altitude of 670 m above sea level. Environmental campaigners have expressed concern at government plans to site an industrial dam on the lake.