Gyvatn is a lake in Agder county, Norway. The lake straddles the borders of the three municipalities of ÃÂ seral, Bygland and Evje og Hornnes. The lake is located about northwest of the village of Byglandsfjord and the lake Byglandsfjorden and it is about east of the village of ÃÂ knes in ÃÂ seral.