Clifford Martin Will (born 1946) is a Canadian born mathematical physicist who is well known for his contributions to the theory of general relativity.
Will was born in Hamilton, Canada. In 1968, he earned a B.Sc. from McMaster University. At Caltech, he studied under Kip Thorne, earning his Ph.D. in 1971. He has taught at the University of Chicago and Stanford University, and in 1981 joined the faculty of Washington University in St. Louis. In 2012 he moved to a faculty position at the University of Florida.
Will's theoretical work has centered on Post-Newtonian expansions of approximate solutions to the Einstein field equation, a notoriously difficult area which forms the theoretical underpinnings essential for such achievements as the indirect verification by Russell Hulse and Joseph Taylor of the existence of gravitational radiation from observations of a binary pulsar.
Will's book reviewing experimental tests of general relativity is widely regarded as the essential resource for research in this area; his popular book on the same subject was listed by New York Times as one of the 200 best books published in 1986.
Will was a Guggenheim Fellow for the academic year 1996–1997. He was elected to the National Academy of Sciences in 2007.