Constantin Piron (1932, Paris - 9 May 2012, Lausanne) was a Belgian physicist who worked for most of his career in Switzerland. In 1963 Piron earned his doctor of science degree from the University of Lausanne under the direction of Ernst Stueckelberg and Josef-Maria Jauch with a thesis on quantum logic, "Axiomatique quantique". He developed Jauch's methods (called the Geneva approach) for the foundations of quantum mechanics. Piron's Theorem (1964) is a famous representation theorem for quantum lattices.