Theon
of Alexandria

Mathematician, editor, and proud dad of Hypatia. Theon of Alexandria (fl. late 4th century CE) was the kind of scholar who didn’t just read Ptolemy — he corrected him. He polished the Almagest, preserved Euclid, and taught astronomy in a world that was getting a little less friendly to science. His legacy is partly his own, partly through Hypatia, but either way: Theon helped keep ancient math alive long enough for it to be reborn.