Thíra or Thera (both: thēr´ə), volcanic island (1991 pop. 9,360), c.30 sq mi (80 sq km), SE Greece, in the Aegean Sea. One of the Cyclades, Thíra is also known as Santorini, for St. Irene, the protector of the island. It is a tourism center noted for its wine. Pumice stone and powdered tufa are exported. It was the site of an enormous ancient volcanic explosion rivaling that of Tambora (and dwarfing that of Krakatoa).
According to tradition, the island was first settled by Phoenicians and later by Laconians under the leader Thera. In the Bronze Age, Thera came under the influence of Crete (see Minoan civilization), but a devastating volcanic eruption (c.1645 BC) buried the island's settlements and threw massive amounts of dust into the earth's atmosphere, affecting the weather worldwide. The island was resettled and later occupied (9th cent. BC) by the Dorians. In 631 BC colonists from the island founded Cyrene in N Africa.
Excavations in the E Mediterranean show that ash from the ancient eruption spread over Anatolia and parts of Egypt, and that the tsunami caused by the eruption reached the shores of what is now Israel. It is theorized by some experts that the effects of the eruption were the catalyst for the collapse of Minoan civilization in the subsequent two centuries. Excavations at a Minoan site on Thíra have uncovered many well-preserved frescoes. Some controversial theories have equated ancient Thera with Atlantis.