Pythagoras

The man who bound a right triangle's three sides into a single rule

Pythagoras was an ancient Greek thinker who believed the order of the world was hidden in numbers themselves, and he led a religious community around that faith. The theorem that bears his name was actually known to the Babylonians long before him, but it was his school that raised it into a universal law — which is why his name stuck. The story that he personally proved it is closer to legend than fact.