Nissedal is a rural municipality in Telemark in the county of Vestfold og Telemark in 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. The municipality of Nissedal was established on January 1, 1838 (see formannskapsdistrikt). As of 2018, Nissedal is home to 1,489 full-time residents and 2,246 vacation homes. The municipality is bordered by Fyresdal to the west, Kviteseid to the north, Drangedal to the east, and Gjerstad, Vegårshei and Åmli municipalities to the south.