Hisøy is a former municipality in the old Aust-Agder county in Norway. The 10-square-kilometre (3.9 sq mi) municipality existed from 1881 until 1992 when it was merged into the municipality of Arendal in what is now Agder county. At the time of its dissolution, it was the smallest municipality in the whole county. The municipality encompassed the islands of Hisøya, Gjervoldsøy, Havsøya, Ærøya, Store Torungen, Lille Torungen, and several other small, unpopulated islands. The administrative centre was the village of Kolbjørnsvik on Hisøya island.

Tromøy is a former municipality in the old Aust-Agder county in Norway. The 30-square-kilometre (12 sq mi) municipality existed from 1878 until its dissolution in 1992. The municipal area is now part of the municipality of Arendal in Agder county. The administrative centre was the village of Brekka, where the historic Tromøy Church is located. The municipality encompassed all of the island of Tromøya as well as many smaller surrounding islands such as Merdø, Gjesøya, Skilsøy, and Tromlingene.