Lysakerelva

Lysakerelven (also known as Lysakerelva, ) is a river in Norway that forms the boundary between the municipalities of the capital city of Oslo and Bærum.

The river by this name has its source in Bogstadvannet, though the source is further up, at Langlivann, and Søndre and Nordre Heggelivann in Oslomarka, the forests surrounding Oslo. Consequently, it is considered part of Oslomarkvassdragene, the river system flowing through these forests, and more specifically Sørkedalsvassdraget, the valley above Bogstadvannet. It flows out into Lysakerfjorden, part of Oslofjorden near Lysaker.