Kos or
Cos (, ) is a
Greek island, part of the
Dodecanese island chain in the southeastern
Aegean Sea, off the Anatolian coast of
Turkey. Kos is the third largest of the Dodecanese by area, after
Rhodes and
Karpathos; it has a population of 33,388 (2011 census), making it the second most populous of the Dodecanese, after Rhodes. The island measures , and is from the coast of the ancient region of
Caria in
Turkey. Administratively, Kos constitutes a municipality within the
Kos regional unit, which is part of the
South Aegean region. The principal town of the island and seat of the municipality is Kos town.