Johannes Hans Daniel Jensen was a German nuclear physicist. During World War II, he worked on the German nuclear energy project, known as the Uranium Club, where he contributed to the separation of uranium isotopes. After the war, Jensen was a professor at the University of Heidelberg. He was a visiting professor at the University of Wisconsin–Madison, the Institute for Advanced Study, University of California, Berkeley, Indiana University, and the California Institute of Technology.

Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter.