Dehradun district () is a district of Uttarakhand state in northern India. The district headquarters is Dehradun, which has also served as the interim capital of Uttarakhand since its founding in 2000. The district has 6 tehsils, 6 community development blocks, 17 towns and 764 inhabited villages, and 18 unpopulated villages. As of 2011, it is the second most populous district of Uttarakhand (out of 13), after Haridwar. Dehradun district also includes the prominent towns of Rishikesh, Mussoorie, Landour and Chakrata. The district stretches from the Ganges river in the east to the Yamuna river in the west, and from the Terai and Shivaliks in the south and southeast to the Great Himalaya in the northwest. During the days of British Raj, the official name of the district was Dehra Dun. In 1842, Dun was attached to Saharanpur district and placed under an officer subordinate to the Collector of the district but since 1871 it is being administered as separate district.