Gjerpen is a former municipality in Telemark county, Norway. The 381-square-kilometre (147 sq mi) municipality existed from 1838 until its dissolution in 1964. The area is now part of Skien Municipality. The administrative centre was the village of Gjerpen, which is now part of the growing town of Skien. Gjerpen Church was the main church for the municipality.

The parish of Gjerpen was established as a municipality on 1 January 1838 (see formannskapsdistrikt law). According to the 1835 census the municipality had a population of 4,381. Gjerpen was located east of the town of Skien. It encompassed districts such as Borgestad, Bøle, Gulset, and Luksefjell. On 1 January 1856, an area of Gjerpen Municipality (population: 1,286) was annexed by the growing town of Skien. On 1 January 1903, an unpopulated area of Saude Municipality was transferred to Gjerpen. Again, on 1 July 1916, another area of Gjerpen Municipality (population: 1,332) was annexed by the growing town of Skien. Then on 1 July 1920, an area of southern Gjerpen (population: 437) was transferred to the town of Porsgrunn.

During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, Gjerpen Municipality (population: 15,300) was merged with the neighboring Solum Municipality (population: 13,706) and the town of Skien (population: 15,805) plus the Valebø area of Holla Municipality (population: 259). These areas became the new Skien Municipality.

The municipality (originally the parish) is named after the old Gjerpen farm (Old Norse: Gerpin; a corruption of Garpvin) since the first Gjerpen Church was built there. The meaning of the first element is unknown. It is possibly the old name of a local river. The river name may have been derived from the word gǫrp which means "the chattering one" or "the chuckling one", likely referring to the noise of the river. The last element is vin which means "meadow" or "pasture".

During its existence, this municipality was governed by a municipal council of directly elected representatives. The mayor was indirectly elected by a vote of the municipal council.

The mayors (Norwegian: ordfører) of Gjerpen (incomplete list):

The municipal council (Herredsstyre) of Gjerpen was made up of representatives that were elected to four year terms. The tables below show the historical composition of the council by political party.

Gjerpen Church (Gjerpen Kirke) is one of the oldest churches in Norway, dating from around the year 1150. Vidkun Quisling was buried in the Gjerpen cemetery.