Úlfljótsvatn is named after Úlfljótr, an important man who was involved in the Alþingi (Icelandic Parliament) in 930.

[citation needed] The lake has an area of 3.6 km² and is situated at an altitude of 80 m. At the deepest point, Úlfljótsvatn is about 34.5 meters deep.

[2] The lake has a water area of 3.6 km² and is located directly south of the larger lake Þingvallavatn on the Sog river, which continues to Álftavatn.

[2] Orkuveita Reykjavíkur bought the rights in 1929-1933 to generate electricity in the upper run of the Sog.

In 1937, the Ljósafoss [ˈljouːsaˌfɔsː] power station was then built, increasing the water level by about 1 metre.