Lierne is a municipality in Trøndelag county, Norway. It is part of the Namdalen region, and it is the largest municipality by area in Trøndelag. The administrative centre of the municipality is the village of Sandvika. Other villages include Inderdal, Mebygda, and Tunnsjø senter. The municipality borders Sweden to the south and east. Most of Lierne lies on the Swedish side of the drainage divide between Norway and Sweden. The municipality is the 16th largest by area out of the 356 municipalities in Norway. Lierne is the 310th most populous municipality in Norway with a population of 1,309. The municipality's population density is and its population has decreased by 7.2% over the previous 10-year period. The municipality of Lierne was established on 1 January 1874 when it was separated from the large municipality of Snaasen. Initially, the population of Lierne was 1,015. On 1 July 1915, it was divided into two municipalities: Nordli (population: 863) in the north and Sørli (population: 739) in the south. This division, however, was short-lived. During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964 they were merged back together again under the former name Lierne. After the merger, there were 2,045 residents in the new municipality. On 1 January 2018, the municipality switched from the old Nord-Trøndelag county to the new Trøndelag county. The municipality (originally the parish) is named after the old name for the region (Hlíð) which means "mountainside" (similar to the Norwegian word li). Historically, the prefix Finna- was often added to the name: Finnahlíð. This prefix is the plural genitive case of finnr which means "Sami person" (or Finn) because the district historically had a significant sami population. Later, the prefix was dropped and the definite plural form of li was used, Lierne. The li name lives on in many places in the municipality such as Nordli and Sørli. The coat of arms was granted on 3 February 1984.