political practice in ancient Athens whereby a prominent citizen who threatened the stability of the state could be banished without bringing any charge against him. (A similar device existed at various times in Argos, Miletus, Syracuse, and Megara.) At a fixed meeting in midwinter, the people decided, without debate, whether they would hold a vote on ostracism (ostrakophoria) some weeks later. Any citizen entitled to vote in the assembly could write another citizen's name down, and, when a sufficiently large number wrote the same name, the ostracized man had to leave Attica within 10 days and stay away for 10 years. He remained owner of his property. Ostracism must be carefully distinguished from exile in the Roman sense, which involved loss of property and status and was for an indefinite period (generally for life).

Ostracism is said by Aristotle, in his Constitution of Athens, to have been introduced by Cleisthenes (Cleisthenes Of Athens) in his reform of the Athenian constitution after the expulsion of Hippias (c. 508 BC), but the first use of it seems to have been made in 488–487 BC, when Hipparchus, son of Charmus of Collytus, was ostracized. After Hipparchus, four more men, the last of them being Aristides, were ostracized before the amnesty in 481, preceding the invasion of Xerxes I. The institution was invoked less frequently after the Persian Wars, falling into disuse after it was used ineffectively, probably in 417, to resolve the political impasse caused by the rivalry of Nicias and Alcibiades. Compare exile and banishment.