Khíos, also Chios, island, eastern Greece, in the Aegean Sea, off the western coast of Asian Turkey. Comprising a department of Greece, the island is 50 km (30 mi) long and up to 24 km (15 mi) wide. The capital and chief town is Khíos, a seaport on the eastern coast. In the north the island is mountainous, but the land in the south is open and fertile. Gum mastic, from which a liqueur is made, and wine are the principal products of the island. Other products include olives, figs, and oranges. Coastal trade is important economically; industries include the mining of antimony and calamite, marble quarrying, and tanning.

The island contains relics of ancient times, when it was an important Greek state, the home of noted poets and sculptors, and a participant in the wars that marked the history of ancient Greece and Rome. Khíos was occupied by the Seljuk Turks in the 11th century ad and later became a possession, successively, of the Venetians, Genoese, and Ottoman Turks. During the Balkan War of 1912, it again became a Greek possession. Population (1981) 50,870.