Tomonaga Sanjūrō (朝永 三十郎, Tomonaga Sanjūrō, 1871–1951) was a Japanese academic and esteemed professor emeritus of medieval, renaissance, early modern, and Kantian philosophy at the University of Kyoto during the early 20th century. He was one of the leading thinkers of the Kyoto School. His son, Shinichirō Tomonaga, is also renowned for receiving the 1965 Nobel Prize in Physics for the development of quantum electrodynamics.