Hessdalen is a village and a 15-kilometre (9.3 mi) long valley in the municipality of Holtålen in Sør-Trøndelag county, Norway. It is located approximately 120 kilometres (75 mi) south of the city of Trondheim, approximately 35 kilometres (22 mi) north of Røros mining town, and about 12 kilometres (7.5 mi) southwest of Ålen/Renbygda. About 150 people live in the valley.
In the central part of the valley is a village area also called Hessdalen. It is where Hessdalen Church is located. The lake Øyungen lies about 7 kilometres (4.3 mi) southwest of the village.
The Hessdalen area is known for the occasional occurrences of sometimes ominous luminous phenomena called the Hessdalen lights. The phenomenon is monitored by the Hessdalen AMS.