Euclid of Megara was a Greek philosopher who lived around the 4th century BCE. He is best known as the founder of the Megarian school of philosophy, which focused on logic and dialectics. His teachings emphasized the importance of definitions and the use of reasoning to arrive at conclusions. Euclid was a student of Socrates and is often associated with the development of dialectical methods. His work influenced later philosophers, including Plato and the Stoics. Although not much of his writing survives, his ideas contributed significantly to the fields of logic and ethics in ancient philosophy.