Margaret Leinen (born September 20, 1946) is an American paleoceanographer and paleoclimatologist. In 2013, Leinen was appointed the 11th director of the Scripps Institution of Oceanography, as well as the dean of the School of Marine Sciences at the University of California, San Diego. She founded the Climate Response Fund, a non-profit focused on enabling better understanding, regulation and responsible use of climate engineering research, and served as its president for a time. For two years, Leinen also worked as chief science officer for a startup company in green technology and climate change mitigation.