Euclid (Greek: . Εὐκλείδης — Eukleidēs), fl. 300 BC, also known as Euclid of Alexandria, is often referred to as the Father of Geometry. He was a Greek mathematician, and is believed to have been active in Alexandria during the reign of Ptolemy I (323 BC–283 BC). His Elements is the most successful textbook in the history of mathematics. In it, the principles of what is now called Euclidean geometry are deduced from a small set of axioms. Euclid also wrote works on perspective, conic sections, spherical geometry, and rigor.
Little is known about Euclid other than his writings. What little biographical information we do have comes largely from commentaries by Proclus and Pappus of Alexandria. Euclid was active at the great Library of Alexandria and may have studied at Plato's Academy in Greece. The date and place of Euclid's birth and the date and circumstances of his death are unknown.
