He is best known for founding Pythagoreanism, a religious and philosophical movement that emphasized the importance of numbers and their connection to the natural world. He is also traditionally associated with the Pythagorean theorem.

The exact circumstances of his death remain uncertain. According to one legend, he was caught in a fire while escaping from enemies and refused to cross a field of beans, which he considered sacred, leading to his death. Other accounts suggest that he died of starvation, was murdered, committed suicide, or simply died of old age. It is generally believed that he fled his school in Croton due to political unrest before his death.