Akerselva or Akerselven is a river which flows through Oslo. It starts at Maridalsvannet in Oslomarka, and traverses the boroughs of Nordre Aker, Sagene, Grünerløkka, central Oslo and Grønland, whereby it finally ends at Paulsenkaien and Oset in Bjørvika. The river is considered to be a part of the Nordmarkvassdraget, and has the Norwegian watercourse number 006.Z. The entire river is about 9.8 kilometres (6.1 mi) long, and has a difference in elevation between source and mouth of approximately 149 metres (489 ft).

Oslo is the capital and most populous city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of 709,037 in 2022, while the city's greater urban area had a population of 1,064,235 in 2022, and the metropolitan area had an estimated population of 1,546,706 in 2021.