Ole J. Kleppa (February 4, 1920 – May 27, 2007) was a Norwegian-born physical chemist and a pioneer and leading authority in the study of metals, molten salts, ceramics and minerals at high temperatures. Kleppa was a professor at the University of Chicago, where he held appointments in the Department of Chemistry, the Department of Geophysical Sciences, the James Franck Institute, and the college. He was the director of the James Franck Institute and the Materials Research Laboratory.