Otto Haxel (2 April 1909, in Neu-Ulm – 26 February 1998, in Heidelberg) was a German nuclear physicist. During World War II, he worked on the German nuclear energy project. After the war, he was on the staff of the Max Planck Institute for Physics in Göttingen. From 1950 to 1974, he was an ordinarius professor of physics at the University of Heidelberg, where he fostered the use of nuclear physics in environmental physics; this led to the founding of the Institute of Environmental Physics in 1975. During 1956 and 1957, he was a member of the Nuclear Physics Working Group of the German Atomic Energy Commission. From 1970 to 1975, he was the Scientific and Technical Managing Director of the Karlsruhe Research Center.