Who overthrew the oligarchy in Athens?

The oligarchy in Athens was overthrown during the 5th century BCE primarily by the leadership of Cleisthenes, often referred to as the "Father of Athenian Democracy." His reforms, enacted around 508-507 BCE, expanded the political power of the citizenry and restructured the political system to reduce the influence of the wealthy elite. This shift laid the foundation for the development of democracy in Athens, allowing broader participation in governance.