Arendal is municipality in the county of Aust-Agder in southeastern Norway. Arendal belongs to the region of Sørlandet.
The administrative centre of the municipality is the city of Arendal. Some of the notable villages in Arendal include Rykene, Eydehavn, Færvik, Strengereid, Kongshavn, Kilsund, Brattekleiv, Longum, Saltrød, Staubø, Vrengen, and Kolbjørnsvik. The offices of GRID-Arendal are also located in the city of Arendal.
The 270-square-kilometre (100 sq mi) municipality is the 288th largest by area out of the 422 municipalities in Norway. Arendal is the 20th most populous municipality in Norway with a population of 44,576. The municipality's population density is 174.7 inhabitants per square kilometre (452/sq mi) and its population has increased by 11.3% over the last decade.