The famous ancient Greek philosopher who taught Alexander the Great was Aristotle. Aristotle, a student of Plato, made significant contributions to numerous fields, including philosophy, science, logic, and ethics. He became Alexander's tutor when Alexander was a young prince, imparting knowledge that would influence the young ruler's later governance and military strategies. Aristotle's teachings emphasized the importance of observation and empirical evidence, laying the groundwork for various scientific disciplines. His impact on Western thought is profound, making him one of the most influential intellectual figures in history.