Karl Ziegler Morgan (September 27, 1907 – June 8, 1999), was an American physicist who was one of the founders of the field of radiation health physics. Late in life, after a long career in the Manhattan Project and at Oak Ridge National Laboratory, he became a critic of nuclear power and nuclear weapons production. Initially at the University of Chicago Metallurgical Laboratory and later in Oak Ridge, Morgan joined a small group of physicists who were interested in the health effects of radiation.