The parish of Tysnæs was established as a municipality on 1 January 1838 (see formannskapsdistrikt). The municipality consists of a group of islands, located south of Bergen where the Hardangerfjord and the coastal archipelago meet. The largest of these islands, named Tysnesøy or just Tysnes, can be reached from the mainland either by ferry to the town of Våge in the north of the island or by the bridge constructed on the eastern side of the island.
The municipality (originally the parish) are named after the Tysnes farm (Old Norse Týsnes), since the first church was built here. The first element is the genitive case of the name of the god Tyr and the last element is Nes which means "headland".