Often called the “Father of Geometry,” Euclid was a teacher of mathematics, cultivating a school of pupils not unlike the style of the Academy.
Euclid likely wouldn’t have reached his level of renown if his works didn’t survive to such an incredible extent. His main work, The Elements, is a proto-textbook of 13 sections pulling together definitions, theories, and constructions of mathematics at the time. He covers geometry, number theory, and incommensurate lines- all subjects that have proved to be invaluable over the development of mathematics.