Bykle is a municipality in Agder county, Norway. It is located in the traditional district of Setesdal. The administrative centre of the municipality is the village of Bykle. Other villages in Bykle municipality include Berdalen, Bjåen, Breive, Hoslemo, Hovden, and Nordbygdi. Bykle was established as a municipality on 1 January 1902 when it was separated from the municipality of Valle.

The 1,467-square-kilometre (566 sq mi) municipality is the 60th largest by area out of the 356 municipalities in Norway. Bykle is the 333rd most populous municipality in Norway with a population of 995. The municipality's population density is 0.8 inhabitants per square kilometre (2.1/sq mi) and its population has increased by 7.1% over the previous 10-year period.

The municipality of Bykle was created when it was separated from the older municipality of Valle on 1 January 1902 after a dispute over the costs of road building (Bykle was the bigger area, while Valle had more people and more money). Initially, Bykle had a population of 476 residents in the new municipality. The boundaries of the municipality have not changed since that time.

The municipality (originally the parish) is named after the old Byklum farm (Old Norse: Byklar) since the first Bykle Church was built there. The farm is named after Lake Bykil, but the meaning of that name is uncertain. The name possibly comes from the word bauka which means "to splash" or "to slosh". Historically, the name has been spelled Bøgle or Bøckle, but the spelling has been Bykle since the 19th century.

The coat of arms was granted on 4 April 1986. The official blazon is "Vert, goutte d'eau" (Norwegian: Grøn grunn strødd med sølv dropar). This means the arms have a green field (background) and the charge is droplets of water that are equally spaced all over the shield. The water droplets have a tincture of argent which means they are commonly colored white, but if it is made out of metal, then silver is used. The green color in the field symbolizes the importance of agriculture in the municipality. The water droplets were chosen as a symbol for the water and rivers in the municipality, as well as for the hydropower plant which was founded in 1915. The plant has brought prosperity to the area since then. The arms were designed by Daniel Rike. The municipal flag has the same design as the coat of arms.

The Church of Norway has one parish (sokn) within the municipality of Bykle. It is part of the Otredal prosti (deanery) in the Diocese of Agder og Telemark.

Bykle sits in the northern part of the Setesdalen valley. It is bordered to the north by Vinje municipality and to the east by Tokke municipality both of which are in Telemark county. It is bordered to the south by Valle and Sirdal municipality, both in Agder county. It is bordered in the southwest by Sandnes municipality and in the west by Hjelmeland and Suldal municipalities–all in Rogaland county.

There are many lakes that are located within the mountainous municipality including Blåsjø, Botsvatn, Hartevatnet, Holmavatnet, Ormsavatnet, Reinevatn, Skyvatn, Store Urevatn, Svartevatnet, and Vatndalsvatnet, and Ytre Storevatnet.