The individual known for his contributions to democracy in ancient Athens is Cleisthenes, often referred to as the "Father of Athenian Democracy." He instituted significant political reforms in 508-507 BC, establishing a system that encouraged citizen participation in governance. Cleisthenes reorganized the social structure, allowing for greater political representation and an early form of direct democracy. His reforms laid the foundation for a more inclusive and participatory political environment, influencing democratic principles that resonate in modern governance today.