Who was Richard Feynman's PhD advisor?

Who was Richard Feynman's PhD advisor? John Archibald Wheeler. Wheeler supervised Feynman's doctoral work at Princeton University, where Feynman completed his PhD in 1942.

Wheeler was a leading theoretical physicist whose interests included gravitation, nuclear physics, and the foundations of quantum mechanics. He encouraged Feynman to investigate a new formulation of electrodynamics based on action principles. That project became the basis of Feynman's dissertation, “The Principle of Least Action in Quantum Mechanics.”

Feynman's thesis explored how quantum mechanics could be formulated using sums over possible histories rather than only the conventional wave-mechanical approach. This work eventually led to the path-integral formulation, one of his most influential contributions to physics.

Wheeler and Feynman also developed the absorber theory of electrodynamics, an attempt to explain electromagnetic radiation through interactions between charges. Feynman later became famous for quantum electrodynamics, particle diagrams, and his work at Los Alamos, but Wheeler remained a formative influence during his graduate years.