Santorini, officially Thira and Classical Greek Thera, is an island in the southern Aegean Sea, about 200 km (120 mi) southeast from the Greek mainland. It is the largest island of a small circular archipelago, which bears the same name and is the remnant of a caldera. It is the southernmost member of the Cyclades group of islands, with an area of approximately 73 km2 (28 sq mi) and a 2021 census population of 15,480. The municipality of Santorini includes the inhabited islands of Santorini and Therasia, as well as the uninhabited islands of Nea Kameni, Palaia Kameni, Aspronisi and Christiana. The total land area is 90.623 km2 (34.990 sq mi). Santorini is part of the Thira regional unit.

The Aegean Sea is an elongated embayment of the Mediterranean Sea between Europe and Asia. It is located between the Balkans and Anatolia, and covers an area of some 215,000 km2 (83,000 sq mi). In the north, the Aegean is connected to the Marmara Sea, which in turn connects to the Black Sea, by the straits of the Dardanelles and the Bosphorus, respectively. The Aegean Islands are located within the sea and some bound it on its southern periphery, including Crete and Rhodes. The sea reaches a maximum depth of 2,639 m (8,658 ft) to the west of Karpathos. The Thracian Sea and the Sea of Crete are main subdivisions of the Aegean Sea.