Frank Kreith (15 December 1922 – 8 January 2018) was an American mechanical engineer.
Born in Vienna, Kreith fled Austria after the annexation of Austria into Nazi Germany in 1938 as a member of the Kindertransport. He obtained degrees from the University of California, Berkeley (1945), the University of California, Los Angeles (1949) and the University of Paris (1965). Kreith worked at the Jet Propulsion Laboratory, received a fellowship from the Daniel and Florence Guggenheim Foundation to study at Princeton University and taught at Berkeley and Lehigh University before becoming a faculty member at University of Colorado Boulder in 1959. He was head of the Solar Thermal Conversion research branch at the Solar Energy Research Institute (SERI) and subsequentely served as the ASME Legislative Fellow at the National Conference of State Legislators, advising lawmakers on energy and environmental issues. Kreith published more than 100 articles in peer-reviewed journals, authored or edited 15 books (among them the seminal textbook Principles of Heat Transfer), and was the Journal of Solar Energy Engineering's editor-in-chief from 1980 to 1987.