Obersaxen (Romansh: Sursaissa) is a municipality in the district of Surselva in the Swiss canton of Graubünden.
Obersaxen is first mentioned in 765 as Supersaxa though this is from a copy which dates from later. In 956 it was mentioned as Supersaxa, and in 1227 as Ubersahse.
The current settlement was founded in the thirteenth century, when a group of German-speaking Walser settled the plateau. Right in the heart of the mainly Romansh-speaking Surselva (which encompasses the valley of the Vorderrhein, along with all of its side valleys, among others the Val Lumnezia), Obersaxen is an island of German-speakers.
Obersaxen has an area, as of 2006, of 61.5 km2 (23.7 sq mi). Of this area, 54.8% is used for agricultural purposes, while 23.4% is forested. Of the rest of the land, 2% is settled (buildings or roads) and the remainder (19.8%) is non-productive (rivers, glaciers or mountains).
The municipality is located in the Rueun sub-district of the Surselva district. It is located on the northern face of the Mundaun mountain chain, on the right side of the Rhine valley. It consists of 28 settlements which are divided into five Pirten around the central village of Meierhof.