Chios is the fifth largest of the Greek islands, situated in the northern Aegean Sea. The island is separated from Turkey by the Chios Strait. Chios is notable for its exports of mastic gum and its nickname is "the Mastic Island". Tourist attractions include its medieval villages and the 11th-century monastery of Nea Moni, a UNESCO World Heritage Site.

Administratively, the island forms a separate municipality within the Chios regional unit, which is part of the North Aegean region. The principal town of the island and seat of the municipality is Chios. Locals refer to Chios town as Chora (literally means land or country, but usually refers to the capital or a settlement at the highest point of a Greek island).

It was also the site of the Chios massacre, in which tens of thousands of Greeks on the island were massacred by Ottoman troops during the Greek War of Independence in 1822.

Midway up the east coast lie the main population centers, the main town of Chios, and the regions of Vrontados and Kambos. Chios Town, with a population of 32,400, is built around the island's main harbour and medieval castle. The current castle, with a perimeter of 1,400 m (4,600 ft), was principally constructed during the time of Venetian and Ottoman rule, although remains have been found dating settlements there back to 2000 B.C. The town was substantially damaged by an earthquake in 1881, and only partially retains its original character.

North of Chios Town lies the large suburb of Vrontados (population 4,500), which claims to be the birthplace of Homer. The suburb lies in the Omiroupoli municipality, and its connection to the poet is supported by an archaeological site known traditionally as "Teacher's Rock".