Castiel ([kɐˈʃtiə̯l]ⓘ) is a former municipality in the district of Plessur in the canton of Graubünden in Switzerland.

Of the rest of the land, 1.8% is settled (buildings or roads) and the remainder (5.9%) is non-productive (rivers, glaciers or mountains).

[5] The age distribution, as of 2000[update], in Castiel is; 24 children or 20.2% of the population are between 0 and 9 years old.

[4] In the 2007 federal election the most popular party was the SVP which received 54.1% of the vote.

[3] The historical population is given in the following table:[2][5] The archeological site of Carschlingg, a prehistoric, late-Roman and Early Middle Ages settlement is listed as a Swiss heritage site of national significance.