Rendalen is a municipality in Hedmark county, Norway. It is part of the traditional region of Østerdalen. The administrative centre of the municipality is the village of Bergset.

The Old Norse form of the name was Reindalr. The first element is the rein old Norsk for reindeer and the last element is dal which means "valley" or "dale". The meaning of the river name is from the valley or vice versa. Renafjellet is one of the other mountains.

The coat-of-arms is from modern times. They were granted on 2 June 1989. The arms show two silver reindeer on a blue background. They symbolize the importance of reindeer farming in the community. The two heads represent the two former municipalities of Øvre Rendal and Ytre Rendal. The arms were designed by the artist Arvid Sveen.

The municipality of Rendalen was established on 1 January 1838 (see formannskapsdistrikt). Rendalen was divided into two separate municipalities (Ytre Rendal and Øvre Rendal) in 1880 when there was a population of 3,529. The two municipalities were reunited on 1 January 1965 and took the name Rendalen.