William L. McMillan (January 13, 1936 – August 30, 1984) was an American physicist noted for his research of condensed matter physics.McMillan was a member of the National Academy of Sciences, Professor of Physics at University of Illinois, Urbana-Champaign.He was also a member of the American Academy of Arts and SciencesMcMillan received the 1978 Fritz London Memorial Prize for his work in superconductors.The National Academies Press called him "the ablest condensed matter physicist of his generation".The University of Illinois established an award in his name: The William L. McMillan Award.