Henri Poincaré (April 29, 1854-July 17, 1912) was one of the greatest French mathematicians and theoretical physicists at the end of the 19th century. Poincaré's contributions to applied mathematics and physics were vast. He made innovations in geometry, differential equation theory, electromagnetism, and topology. He was the first person to discover a chaotic deterministic system, one of the foundations of modern chaos theory.