Introduction
Greek island in the Aegean Sea This article is about the Greek island. For Apple's operating system, see iOS. For other uses, see IOS (disambiguation). Municipality in GreeceIos Ίος, ΝιόςMunicipalityClockwise from top: Church of Saint Irene, Odysseas Elytis Theatre, Cathedral Church Of Ios, Chora Hill, Windmills in Chora SealIosCoordinates: 36°43′0″N 25°20′11″E / 36.71667°N 25.33639°E / 36.71667; 25.33639CountryGreeceAdministrative regionSouth AegeanRegional unitThiraMunicipality established1835SeatChoraGovernment • MayorGkikas GkikasArea • Municipality109.0 km2 (42.1 sq mi)Highest elevation713 m (2,339 ft)Lowest elevation0 m (0 ft)Population (2021) • Municipality2,299 • Density21.09/km2 (54.63/sq mi)Demonym(s)Ιήτης (Iitis) (official)Ιέτης (Ietis) (Ancient Alternative)Νιώτης (Niotis) (local) Iitian or Ietian (anglicised)Time zoneUTC+2 (EET) • Summer (DST)UTC+3 (EEST)Postal code840 01Area code22860Vehicle registrationEMWebsiteios.gr Map of Ios Ios (also spelled Io or Nio; Greek: Ίος, Greek pronunciation: [ˈi.os]; Ancient Greek: Ἴος [í.os]; locally Nios, Νιός) is a Greek island in the Cyclades group in the Aegean Sea. The island is largely hilly, with cliffs descending steeply to the sea on most sides. It is situated halfway between Naxos and Santorini. Ios measures about 18 kilometres (11 miles) in length and 10 kilometres (6 miles) in width, and covers an area of 109.024 square kilometres (42.094 sq mi). Its population was 2,299 in the 2021 census (down from 3,500 in the 20th century). Ios is part of the Thira regional unit.