Tiefencastel (Romansh: Casti) is a village and a former municipality in the district of Albula in the canton of Graubünden in Switzerland.

Of the rest of the land, 3.1% is settled (buildings or roads) and the remainder (27%) is non-productive (rivers, glaciers or mountains).

Most of the population (as of 2000[update]) speaks German (58.3%), with Romansh being second most common language (37.8%) and Italian the third ( 1.3%).

[4] The age distribution, as of 2000[update], in Tiefencastel is; 37 people or 16.1% of the population are between 0 and 9 years old.

The wettest month is August during which time Tiefencastel receives an average of 110 mm (4.3 in) of precipitation.

The driest month of the year is February with an average of 35 mm (1.4 in) of precipitation over 10.8 days.

On 13 August 2014, a passenger train was struck by a landslide and derailed a kilometre west of the station.