Mastrils is a former municipality in the district of Landquart in the Swiss canton of Graubünden.

Of the rest of the land, 2.5% is settled (buildings or roads) and the remainder (4.9%) is non-productive (rivers, glaciers or mountains).

[3] The municipality is located in the Fünf Dörfer sub-district of the Landquart district.

Most of the population (as of 2000[update]) speaks German (93.0%), with Italian being second most common ( 1.9%) and Romansh being third ( 1.5%).

[6] The age distribution, as of 2000[update], in Mastrils is; 54 children or 10.2% of the population are between 0 and 9 years old.

[5] In the 2007 federal election the most popular party was the SVP which received 35.8% of the vote.