Nissedal is a rural municipality in Telemark region of Vestfold og Telemark county, Norway. It is part of the traditional regions of Upper Telemark and Vest-Telemark. The administrative centre of the municipality is the village of Treungen. Other villages in Nissedal include Kyrkjebygda and Felle. The municipality is the 129th largest by area out of the 356 municipalities in Norway. Nissedal is the 303rd most populous municipality in Norway with a population of 1,414. The municipality's population density is and its population has decreased by 1.1% over the previous 10-year period. Nissedal is also notable in that it has 2,246 vacation homes, so the population swells during holidays and vacation times. Nissedal has been nicknamed the "Telemark Riviera" due to its close proximity to Gautefall Alpine Center, and due to its many campgrounds and places for outdoor activities. There is a total of 1,750 lakes in Nissedal, including Nisser, the seventh-largest lake in Norway, which Nissedal is named after. Gautefall, which is home to Telemark County’s largest alpine center, lies adjacent to the municipality. For residents of cities near the Oslo Fjord, Gautefall is the nearest winter sport destination. Nissedal’s terrain is characterized by roche moutonnée rock formations, mountains, valleys, forests, wetlands, and lakes. Nissedal is a popular destination for outdoor activities such as paddling, fishing, swimming, mountain biking, hiking, kayaking, skiing, boating, and more. It is recognized as one of Norway’s best places for mountain climbing. Nissedal is home to Hægefjell, one of Norway’s most popular mountain climbing destinations. Nissedal was originally a part of the Kviteseid parish until Nissedal established its own parish in 1810. The parish of Nissedal was established as a municipality on 1 January 1838 (see formannskapsdistrikt law). During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee.