The person known as the "father of geometry" is Euclid. He was a Greek mathematician who lived around 300 BC and is famous for his work "Elements," which systematically laid out the principles of geometry in a logical and deductive way. Euclid's work has been foundational in the field of geometry and has influenced mathematical education for over two thousand years. His approach to geometry, now called Euclidean geometry, remains a fundamental part of mathematics today.