Haltdalen (historically: Holtaalen) is a former municipality in the old Sør-Trøndelag county, Norway. The 509-square-kilometre (197 sq mi) municipality existed from 1838 until 1972 when it was merged with Ålen to become the present-day municipality of Holtålen in Trøndelag county. The administrative centre of the municipality was the village of Haltdalen where the Haltdalen Church is located.

The prestegjeld of Holtaalen was established as a civil municipality on 1 January 1838 (see formannskapsdistrikt). In 1841, the western part of the municipality (population: 1,272) was separated to become the new municipality of Singsaas. This left Holtaalen with 1,885 residents. Then in 1855, the southeastern part of Holtaalen (population: 1,487) was separated to become the new municipality of Aalen. This left Holtaalen with 809 residents. In 1917, the spelling of the name was changed to Holtålen. In 1937, the name was changed from Holtålen to Haltdalen. Starting in the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1972, the neighboring municipalities of Haltdalen (population: 778) and Ålen (population: 1,944) were merged to form the new municipality of Holtålen.

The municipality (originally the parish) was first named Holtaalen. The first element of the name comes from the local river Holta, a side branch of the larger Gaula River. The last element is áll which means "narrow river channel" (like an eel). On 21 December 1917, a royal resolution enacted the 1917 Norwegian language reforms. Prior to this change, the name was spelled Holtaalen with the digraph "aa", and after this reform, the name was spelled Holtålen, using the letter å instead.

On 15 October 1937, a royal resolution changed the name of the municipality to Haltdalen, effective 1 January 1938. The first element of the new name came from the same river name as before. The last element comes from dalr which means "valley" or "dale". The municipality kept this name until 1972 when the municipality was merged with the neighboring municipality of Ålen to form the new municipality of Holtålen, resurrecting the old name of the municipality that was used before 1937.

While it existed, this municipality was responsible for primary education (through 10th grade), outpatient health services, senior citizen services, unemployment, social services, zoning, economic development, and municipal roads. During its existence, this municipality was governed by a municipal council of elected representatives, which in turn elected a mayor.

The mayors of Haltdalen:

The municipal council (Herredsstyre) of Haltdalen was made up of representatives that were elected to four year terms. The party breakdown of the final municipal council was as follows:

• List of former municipalities of Norway