Romsdalen is a valley in the western part of Norway. The 60-kilometre (37 mi) long valley runs through Rauma Municipality in Møre og Romsdal county and Lesja Municipality in Innlandet county. It is the valley of the Rauma river, from Old Norse word Raumsdalr which means 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.

A valley is an elongated low area often running between hills or mountains, which typically contains a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a very long period. Some valleys are formed through erosion by glacial ice. These glaciers may remain present in valleys in high mountains or polar areas.