Lesvos  is a Greek island located in the northeastern Aegean Sea, often called Mytilene (Μυτιλήνη) in Greece, after its capital. It has an area of 1,633 km² (631 sq mi) with 321 kilometres (199 miles) of coastline, making it the third largest island in Greece. It is separated from Turkey by the narrow Mytilini Strait and in late Palaeolithic/Mesolithic times was joined to the Anatolian mainland before the end of the Last Glacial Period.

Lesbos is also the name of a regional unit of the North Aegean region, within which Lesbos island is one of five governing islands. The others are Chios, Ikaria, Lemnos, and Samos. The North Aegean region governs nine inhabited islands: Lesbos, Chios, Psara, Oinousses, Ikaria, Fournoi Korseon, Lemnos, Agios Efstratios and Samos. The capital of the North Aegean Region is Mytilene. The population of Lesbos, which sometimes is called the Island of the Poets, is approximately 100,000, a third of whom live in its capital, Mytilene, in the southeastern part of the island. The remaining population is distributed in small towns and villages. The largest are Plomari, Kalloni, the Gera Villages, Agiassos, Eresos, and Molyvos (the ancient Mythimna).