Kenneth Tompkins Bainbridge (July 27, 1904 - July 14, 1996) was an American physicist at Harvard University who did work on cyclotron research. His precise measurements of mass differences between nuclear isotopes allowed him to confirm Albert Einstein's mass-energy equivalence concept. He was the Director of the Trinity test of the Manhattan Project, which took place July 16, 1945. This marked the beginning of his dedication to ending the testing of nuclear weapons and to efforts to maintain civilian control of future developments in that field. Bainbridge returned to Harvard after the war. From 1950-1954, he chaired the physics department at Harvard. During those years, he drew the ire of Senator Joseph McCarthy for his aggressive defense of his colleagues in academia. Throughout the 1950s, Bainbridge remained an outspoken proponent of civilian control of nuclear power and the abandonment of nuclear testing. In 1976, Bainbridge retired from Harvard. He died in 1996 at the age of 91.