Beiarn is a municipality in Nordland county, Norway. It is part of the Salten region and the Bodø Region. The administrative centre of the municipality is the village of Moldjord. Beiarn was separated from Gildeskål in 1853.It is located just north of the Arctic Circle, on the Beiarelva river in Beiardalen (valley), and the area offers many outdoor activities to visitors, including fishing, caving and mountain walking. The river is one of the best salmon rivers in North Norway. Beiarn farm museum includes an overview of Beiarn's cultural history, from the Viking age through to the middle of the last century.
The World's most northern naturally occurring elm forest (Ulmus glabra) grows in Arstadlia nature reserve, where the rich vegetation also includes orchids. Beiarn is part of the Bodø Region, a statistical metropolitan region. Beiarn is one of two Norwegian municipalities that do not have any non-western immigrants as of 1 January 2008.The Old Norse form of the name was (probably) Beðir. The meaning of the name is unknown. (Maybe related to the English word bed in the sense 'river bed'.)