Cleisthenes  was a noble Athenian of the Alcmaeonid family. He reformed the constitution of Athens, and set it on a democratic footing in 508/7 BC. For these accomplishments, historians refer to him as "the father of Athenian democracy". He also increased the power of the Assembly, and he broke up power of the Athenian nobility.
With help from the his clan, he overthrew Hippias the tyrant (dictatorial ruler). After the collapse of Hippias' tyranny, Isagoras and Cleisthenes were rivals for power, but Isagoras won the upper hand by appealing to the Spartan king Cleomenes I to help him expel Cleisthenes.
So Cleisthenes left Athens as an exile, and Isagoras held power in the city. Isagoras uprooted hundreds of people from their homes on the pretext that they were cursed, and attempted to dissolve the Council (βουλή, boulé). However, the Council resisted, and the Athenian people declared their support of it. Hence Isagoras and his supporters were forced to flee to the Acropolis, remaining besieged there for two days. On the third, they fled and were banished. Cleisthenes was subsequently recalled, along with hundreds of exiles, and he assumed leadership of Athens.
- Greek: Κλεισθένης; and Kleisthenes is a good spelling of the name in English. The Greek alphabet has no 'C', and the Latin alphabet had no 'K'. From this we see that any Greek word containing a 'C' has been 'translated' into Latin, or an Italic language. The last 'e' in the name is a long e, and this is sometimes written as Kleisthenês.
- Ober, Josiah 2007. "I besieged that man, Democracy's revolutionary start". in Origins of Democracy in Ancient Greece. University of California Press. ISBN 978-0520245624. p83 ff.
- R. Po-chia Hsia, Lynn Hunt, Thomas R. Martin, Barbara H. Rosenwein, and Bonnie G. Smith, 2007. The making of the West: peoples and cultures, a concise history, volume I: to 1740 Boston and New York: Bedford/St. Martin’s. p44
- Aristotle, Constitution of the Athenians, Chapter 20