Arne RSPB reserve is a 5.634-square-kilometre (1,392-acre) nature reserve and Site of Special Scientific Interest (SSSI) maintained by the RSPB and located in Dorset. It was notified as an SSSI in 1986 and the estuarine reedbeds within the site are designated as a national nature reserve. The reserve occupies the Arne Peninsula, which protrudes into Poole Harbour. Adjacent to the site is the village of Arne, although the nearest major settlement is the town of Wareham. Over 500 species of vascular plant have been recorded on the reserve since 1966.