Cleisthenes

Cleisthenes, with the support of the Alcmaeonid family and Spartan assistance, led the overthrow of the tyrant Hippias, son of Peisistratus. This ended the Peisistratid tyranny in Athens and opened the way for democratic reforms.

Cleisthenes reorganized the Athenian citizen body into ten new tribes based on demes, replacing the old four Ionian tribes. He established the Council of 500 (Boule) and introduced ostracism, creating a system of isonomia (equal rights) that is considered the foundation of Athenian democracy.

Cleisthenes instituted ostracism, a procedure allowing Athenian citizens to vote annually to exile a prominent citizen deemed a threat to democracy for ten years. This mechanism aimed to prevent the rise of a new tyrant and stabilize the democratic system.