The siege of Melos occurred in 416 BC, during the Peloponnesian War between Athens and Sparta, when the Athenians attacked Melos, an island in the Aegean Sea roughly 110 kilometres (68 miles) east of mainland Greece. Though the Melians had ancestral ties to Sparta, they were neutral in the war. Athens invaded Melos in the summer of 416 BC and demanded that the Melians surrender and pay tribute to Athens or face annihilation. The Melians refused, so the Athenians laid siege to their city. Melos surrendered in the winter, and the Athenians executed the men of Melos and enslaved the women and children.
This siege is best remembered for the Melian Dialogue, a dramatization of the negotiations between the Athenians and the Melians before the siege, written by the classical Athenian historian Thucydides. In the negotiations, the Athenians offer no moral justification for their invasion, but instead bluntly tell the Melians that Athens need Melos for its own ends and that the only thing Melians stand to gain in submitting without a fight was self-preservation.