Cleisthenes (/ˈklaɪsθɪˌniːz/; Greek: Κλεισθένης, Kleisthénēs; also Cleisthenes or Cleisthenes) was an ancient Athenian lawgiver credited with reforming the constitution of ancient Athens and setting it on a democratic footing in 508 BC. For these accomplishments, historians refer to him as "the father of Athenian democracy. He was a member of the aristocratic Alcmaeonid clan, and the maternal grandson of the tyrant Cleisthenes of Sicyon, as the younger son of the latter's daughter Agariste and her husband Megacles. He was also credited with increasing the power of the Athenian citizens' assembly and for reducing the power of the nobility over Athenian politics. In 510 BC, Spartan troops helped the Athenians overthrow their king, the tyrant Hippias, son of Peisistratos. Cleomenes I, king of Sparta, put in place a pro-Spartan oligarchy headed by Isagoras. But his rival Cleisthenes, with the support of the middle class and aided by democrats, took over. Cleomenes intervened in 508 and 506 BC, but could not stop Cleisthenes, now supported by the Athenians. Through Cleisthenes' reforms, the people of Athens endowed their city with isonomic institutions—equal rights for all citizens (though only men were citizens)—and established ostracism.
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