Who is credited with being the father of geometry?

Euclid is credited with being the father of geometry. The ancient Greek mathematician, who flourished around 300 BC in Alexandria, is best known for writing the Elements, a thirteen-book work that organized geometry into definitions, postulates, propositions, and proofs.

Euclid did not invent every idea in the Elements. He drew on earlier mathematicians, including Thales, Pythagoras, Eudoxus, Hippocrates of Chios, and Theaetetus. His lasting achievement was arranging much of that knowledge into a logical, deductive system. This approach made geometry teachable and gave later mathematicians a model for rigorous proof.

The geometry based on his system is called Euclidean geometry. It dominated mathematical education for centuries, although the discovery of non-Euclidean geometries in the 19th century showed that alternative systems could be built by changing assumptions such as the parallel postulate. A common mix-up is confusing Euclid with Euclid of Megara, a different Greek philosopher associated with Socrates.