Romsdalen is a valley in Norway. The long valley runs through Rauma Municipality in Møre og Romsdal county and Lesja Municipality in Oppland county. It is the valley of the Rauma river, from old norse Raumsdalr (Rauma valley). The traditional district of Romsdal, which makes up about one-third of Møre og Romsdal county, is named for the valley of Romsdalen. The main road E136 and the Rauma line runs along the valley floor.