Lesbos (Λέσβος) is a prefecture of Greece, part of the periphery North Aegean.

It is also the name of its main island, which is also called Mytilene. This is in the Aegean Sea near Turkey. The second largest island is Lemnos, to the northwest.

In modern Greek, the island's name is Lesvos and its inhabitants are thus named Lesvonians or Lesviots (rather than "Lesbians").

Principal towns on the island are Mytiline (the capital), Kalloni, Mithymna, Plomari, Agiassos, Petra.

The island has been inhabited since the Bronze Age. It is first mentioned in Hittite records as Lazpa. Other ancient names are: Lassia, Imerti, Aegira, Issa, Mytonis, and Les-Ba.

Lesbos was the center of civilization in the 6th century BCE; as it was home to the poets Sappho and Alcaeus. In 428 BCE, Lesbos joined the Delian League in an unsuccessful revolt against Athens. Aristotle and Epicurus lived here once as well.

In Greek mythology, "Lesbos" was also the name of the patron god of the island. Lesbos was son of Lapithes and he married Methymna.

The word "lesbian" is derived from the island's name. This originates in the poems of Sappho of Lesbos, where love between women was described. Due to this link, Lesbos has often been the destination of cruises and other vacations for lesbians; however, Lesbonian authorities have expressed annoyance at this, with some cruise ships being denied permission to dock.

On the south coast of Lesbos is the pretty coastal town of Plomari, where it is said that the finest ouzo in the world is made to this day in traditional copper stills.

At the western tip of the island is the small fishing village of Sigri, close to which is the world's largest petrified forest, estimated to be about twenty million years old.