Mysen is the administrative center of the municipality of Eidsberg in the county of Østfold in Norway.
The town is named after the old farm of Mysen (Norse Mysin, from *Mosvin), since the town is built on its ground. The first element is mosi m 'bog, marsh', the last element is vin m 'meadow, pasture'.
Between 1920 and 1961, it was a separate municipality. Mysen became an independent municipality on 1 July 1920 when it was spun off from Eidsberg. On 1 January 1961 Mysen was merged again with Eidsberg. As with many other places in Eastern Norway Mysen has grown up around a railway station, after Østfold Line's Eastern Line opened in 1882. Today the station is an end stop for most local trains on the eastern line. Therefore, Mysen is a communication center for inner Østfold, with bus routes to most of the surrounding area, also Töcksfors in Sweden. The village had 6,084 inhabitants as of 1 January 2011.
During the Second World War. there was a Nazi concentration camp at Mysen. One camp commandant was Hans Aumeier, who was later tried and convicted at the Auschwitz Trial.
Coordinates: 59°33′N 11°20′E / 59.550°N 11.333°E