Mosjøen (Southern Sami: Mussere) is a town, a former town municipality, and a former privileged staple place in the Municipality of Vefsn in the southern part of the County of Northland, Norway. Established in 1875, Mosjøen is the oldest town in the Helgeland region, and only Bodø is older within Nordland. The village has a population (2013) of 9,665, giving it a population density of .