Theon of Alexandria (Θέων ὁ Ἀλεξανδρεύς) was a Greek mathematician and astronomer of the 4th century CE, active in Alexandria during the reigns of Theodosius I and Arcadius [2][3]. He held a position at the Museum, Alexandria's institution of higher learning, and is noted as its last attested member [1]. He is most widely remembered as the father and teacher of the philosopher Hypatia [1].

His scholarly output consisted of influential commentaries and editions of foundational texts. Theon produced the standard commentary on Ptolemy's Almagest and a definitive edition of Euclid's Elements, which included his own notes and alternative proofs [1][2]. He also wrote a commentary on Ptolemy's Handy Tables and a treatise on the astrolabe [1][2].

Theon played a crucial role in preserving and transmitting classical Greek mathematics and astronomy. His editions, which incorporated corrections and updates, became essential textbooks for Byzantine, Islamic, and later scholars [1][2]. He serves as a vital link between antiquity and the medieval period, both through his widely circulated works and through his famous daughter, Hypatia [1][3].

Sources 1. Stanford Encyclopedia of Philosophy (Theon of Alexandria): https://plato.stanford.edu/entries/hypatia/#Theo 2. Encyclopædia Britannica (Theon of Alexandria): https://www.britannica.com/biography/Theon-of-Alexandria 3. Perseus Digital Library (Smith's Dictionary of Greek and Roman Biography and Mythology, "Theon"): http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0104%3Aentry%3Dtheon-bio-1