John Hasbrouck van Vleck (March 13, 1899 – October 27, 1980) was an American physicist. Born in Middletown, Connecticut, and growing up in Madison, Wisconsin, he went to Harvard for college and graduate school. He joined the University of Minnesota as an assistant professor in 1923, then moved to the University of Wisconsin before settling at Harvard. Van Vleck developed fundamental theories of the quantum mechanics of magnetism and the bonding in metal complexes (crystal field theory).
For his contributions to the understanding of electrons in non-crystalline magnetic solids, van Vleck was awarded the 1977 Nobel Prize in Physics, along with Philip W. Anderson and Sir Nevill Mott.
