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.