Cazis(Romansh: Tgazas) is a municipality in the Viamala Region in the Swisscanton of Graubünden. On 1 January 2010 the municipalities of Portein, Präz, Sarn and Tartar merged into the municipality of Cazis.
Cazis is first mentioned in 926 as Cacias.
Cazis has an area, as of 2006[update], of 7.3 km2 (2.8 sq mi). Of this area, 41% is used for agricultural purposes, while 41.1% is forested. Of the rest of the land, 13.6% is settled (buildings or roads) and the remainder (4.3%) is non-productive (rivers, glaciers or mountains).
Before 2017, the municipality was located in the Thusis sub-district, of the Heinzenberg district, after 2017 it was part of the Viamala Region. It is located on the western side of the Hinterrhein valley. It consists of the linear village of Cazis and the hamlets of Ober- and Unterrealta, Luvreu, Ratitsch, Summaprada, Schauenberg and Valleina. The municipalities of Cazis, Portein, Präz, Sarn, and Tartar merged on 1 January 2010 into a new municipality that will be known as Cazis.