Philip Morrison, (7 November 1915 in Somerville, New Jersey – 22 April 2005 in Cambridge, Massachusetts) was Institute Professor Emeritus and Professor of Physics Emeritus at the Massachusetts Institute of Technology (MIT).

Morrison grew up in Pittsburgh and graduated from its public schools. He earned his B.S. in 1936 at the Carnegie Institute of Technology and in 1940 he earned his Ph.D. in theoretical physics at the University of California, Berkeley, under the supervision of J. Robert Oppenheimer.

In 1942 he joined the Manhattan Project as group leader and physicist at the laboratories of the University of Chicago and Los Alamos. He was also an eyewitness to the Trinity test, and helped to transport its plutonium core to the test site.

After surveying the destruction left by the use of the atom bomb in Hiroshima, Morrison became a champion of nuclear nonproliferation. He helped found the Federation of American Scientists, wrote for the Bulletin of Atomic Scientists, and helped to found the Institute for Defense and Disarmament Studies. He was also a vocal critic of the Strategic Defense Initiative.

In May 1953 Dr. Morrison testified before the Subcommittee to Investigate the Administration of the Internal Security Act. When asked if he had ever been a member of the Communist Party (CPUSA), Morrison replied: "I joined the Young Communist League when I was 18, and when I was 21 (1936) I did become a member of the Communist party in Berkeley. I don't remember precisely which branch."

Morrison joined the physics faculty at Cornell University in 1946 and would move on to MIT in 1964. In 1959, Morrison and Giuseppe Cocconi published a paper proposing the potential of microwaves in the search for interstellar communications, a component of the modern SETI program.

Morrison was also known for his numerous books and television programs, including Powers of Ten (1968) and the 1987 PBS series The Ring of Truth: An Inquiry into How We Know What We Know[8][9], which he also hosted. In addition, he was a reviewer of books on science for Scientific American since 1965.

Morrison was a fellow of the American Physical Society and chairman of the Federation of American Scientists from 1973 to 1976. He was also a member of the National Academy of Sciences, the International Astronomical Union, the American Association of Physics Teachers, the American Academy of Arts and Sciences and the American Philosophical Society.

The Astronomical Society of the Pacific gave him the Klumpke-Roberts Award in 1992.