Santorini, officially Thira or Thera, is a Greek island in the southern Aegean Sea, about 125 mi (201 km) southeast from the mainland. It is the largest island of a small, circular archipelago formed by the Santorini caldera. It is the southernmost member of the Cyclades group of islands, with an area of approximately 28 sq mi (73 km2) and a 2021 census population of 15,480. The municipality of Santorini includes the inhabited islands of Santorini and Therasia, and the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi, Anydros, and Christiana. The total land area is 35 sq mi (91 km2). Santorini is part of the Thira regional unit.