Arna is a former municipality in Hordaland county, Norway. The municipality existed from 1964 until 1972. It encompassed the northeastern part of the Bergen Peninsula, along the Sørfjorden, bordering the city of Bergen across the mountains to the west. The administrative centre of the municipality was the village of Indre Arna. The municipality stretched from Ytre Arna to Trengereid along the coast and then inland about 8 kilometres (5.0 mi) to the Espeland area.