Ole Jakob Kleppa (February 4, 1920 – May 27, 2007) was a Norwegian–American physical chemist and a pioneer and leading authority in the study of metals, molten salts, ceramics and minerals at high temperatures.

After completing secondary school, Kleppa received his Master of Science degree in chemical engineering in 1946 and his Ph.D. in 1956 from the Norwegian Institute of Technology.

After a year of teaching chemistry and physics in Uppsala, Sweden he flew to Great Britain, where he served in the Norwegian Army as an Intelligence Officer.

One of his primary achievements was the development of the Kleppa calorimeter, an instrument that measures tiny amounts of heat as new materials form at high temperatures.

[2] The alloys, minerals, and compounds that Kleppa collected and interpreted data on has been widely used in the aviation industry and by physicists developing superconducting materials for advanced technological applications including nuclear reactors.

He was a friend and colleague of R. Stephen Berry, Stuart Rice, Robert Gomer, Thomas Rosenbaum, and Nobel Laureates Yoichiro Nambu and Subrahmanyan Chandrasekhar.