Mjøndalen is the administrative centre of Nedre Eiker municipality in Buskerud county, Norway. It is situated south of the Drammenselva River opposite of Krokstadelva.
Mjøndalen has traditionally been a railway site most known as an industrial sawmill location. Historically Mjøndalen was known for its industry; including paper & pulp production and a substantial cellulose industry. The production of wood products and furniture are also traditional commercial activities. All the paper mills closed in the late 1960s and early 1970s.
Mjøndalen has a friendly sports rivalry with the neighbouring communities of Solbergelva and Krokstadelva. The rivalry is mostly in sports such as soccer and bandy and cross-country skiing. In bandy, Mjøndalen IF have become Norwegian champions several times.
Portåsen – Wildenveys Rike is a centre honouring the life and writing of Herman Wildenvey, a prominent Norwegian poet. Herman Wildenvey lived the first three years of his life in Mjøndalen. At three years of age, he was moved to the Portåsen farm on the edge of the forest above the village.
Today Portåsen is a meeting place and venue for local, regional and national artists. The site includes a newly renovated farmhouse and farm buildings. Stiftelsen Portåsen is the organization which works on the development of Portåsen.
Coordinates: 59°45′N 10°01′E / 59.750°N 10.017°E