Langonnet (Breton: Langoned) is a commune in the Morbihan department of Brittany in north-western France.

Thus, the main language was Breton until the advent of intensive farming after the Second World War, at which point the population, previously bilingual, switched to French.

The highest point of the parish is the calotte Saint Joseph, a round hill whose top is 292 meters above sea level.

The commune's name is written "Langoned" in modern Breton but has been spelled in various ways through the years due to various attempts to transcribe the Breton phonetic system into the Latin alphabet: The name is said to come from "Lann-Conet", the monastery ("lan" in Breton; compare Welsh "llan", as in Llanelli) of Conet[4] (or Conoit, Konoed, Kon(n)ed, Konoid = Cynwyd, Kynwyd or Kynyd in Welsh), a Welsh saint who was active in Brittany.

The municipality launched a linguistic plan through Ya d'ar brezhoneg on 27 January 2005.