Leonard Susskind is the Felix Bloch Professor of Theoretical Physics at Stanford University, and Director of the Stanford Institute for Theoretical Physics. He received a BS in physics from City College of New York and a PhD from Cornell University.

He is a member of the National Academy of Sciences, and the American Academy of Arts and Sciences, an associate member of the faculty of Canada's Perimeter Institute for Theoretical Physics, and a distinguished professor of the Korea Institute for Advanced Study. Susskind is widely regarded as one of the fathers of string theory, having, with Yoichiro Nambu and Holger Bech Nielsen, independently introduced the idea that particles could in fact be states of excitation of a relativistic string. He was the first to introduce the idea of the string theory landscape in 2003. He was awarded the 1998 J. J. Sakurai Prize.

Susskind was an Assistant Professor of Physics, then an Associate Professor at Yeshiva University (1966–1970), after which he went for a year at the University of Tel Aviv (1971–72), returning to Yeshiva to become a Professor of Physics (1970–1979). In 2007, Susskind joined the Faculty of Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, as an Associate Member. He is also a distinguished professor at Korea Institute for Advanced Study.