Portein (Romansh: Purtagn) was a municipality in the district of Hinterrhein in the Swiss canton of Graubünden.

[1] In Silver (white) an upright, red armed black bear carrying a gold tree trunk.

Of the rest of the land, 2% is settled (buildings or roads) and the remainder (8.2%) is non-productive (rivers, glaciers or mountains).

[3] The municipality is located in the Thusis sub-district, of the Hinterrhein district in the Heinzenberg.

It is located on a ridge between the Porteiner Tobel and the Val da la Malanotg at an altitude of 1,178 m (3,865 ft).

The municipalities of Portein, Präz, Sarn, and Tartar merged on 1 January 2010 into Cazis.