Lüen is a former municipality in the district of Plessur in the canton of Graubünden in Switzerland . On 1 January 2013 the former municipalities of Lüen, Calfreisen , Castiel, Langwies , Molinis , Peist and St. Peter-Pagig merged into the municipality of Arosa .

Lüen is first mentioned in 1084 as Leune.

Before the merger, Lüen had a total area of 3.5 km2 (1.4 sq mi). Of this area, 37% is used for agricultural purposes, while 52.3% is forested.