Pythagoras was a Greek mathematician, philosopher, and mystic. He is best known for the similarly named theorem.
He did most of his work in southern Italy and wrote nothing down.
Pythagoras was a sage who founded a small religion of devoted followers.
While he probably didn't prove the theorem that bears his name, he is said to have known “the truth of the theorem" and made an enormous sacrifice to the gods in honor of the discovery.
His mystical approach to numbers also lead him to discover the relationships between harmonic notes in music and attempt to describe the world regarding math; an activity science carries on to this day.