According to mythology, Ios was the birthplace of Homer's mother, and it is believed that the great poet was buried here.
The island's old name was Phoeniki because of the Phoenicians, its first settlers. It took its present name from the Ionians, who settled it later.
During classical times, Ios was a member of the Athenian League. In Roman times it fell into oblivion and served as a place of exile. In 1207, it was taken by the Venetians and became part of the Duchy of Naxos.
In 1550, it passed into the possession of the Turks. It made a major contribution to the Greek War of Independence of 1821 under the leadership of Panagiotis Amiridakis. It was finally liberated in 1830 by the Treaty of London along with the rest of the Cyclades.