Ostracon (Greek: ὄστρακον, plural ὄστρακα, ostraca, or ostraka).

One of the more controversial policies of Athenian democracy was Ostracism. This blunt instrument of the state allowed its citizens to vote for the ten-year expulsion from the city of a person they deem dangerous or undesirable.

In many cases prominent Athenian citizens with valuable contributions to the state were forced to leave Athens. In many cases citizens would ostracize a citizen out of fear that they might have amassed too much political power or influence, and in many more cases they became the victims of overzealous political opponents.

Themistocles, the hero of the Persian Wars is one striking example of a prominent Athenian citizen who despite his contributions was forced to leave Athens and to die in exile.