Kenneth Bainbridge (1904-1996) was an American physicist.
In September 1940, Bainbridge was the first physicist to be recruited by Ernest Lawrence to the microwave "radio location" project that became the Radiation Laboratory at MIT. His experience at the Cavendish Laboratory at Cambridge was an asset as this activity had begun in close collaboration with British scientists. He oversaw the development of radars of increasing power especially for the Navy. In the spring of 1941, he made a visit to Britain under wartime conditions to observe and report on secret developments there, and learned about British studies for nuclear energy in addition to radar.
In May 1943, Bainbridge was recruited to the nuclear weapons laboratory, “Project Y”, at Los Alamos. He oversaw the first explosion of a nuclear device, the Trinity test. Following the fearsomely successful explosion early in the morning of July 16, 1945, he congratulated J. Robert Oppenheimer and the others, then made his legendary remark, "Now we are all sons of bitches." Oppenheimer later remarked that this was the best thing anyone had said just after the test.
Bainbridge subsequently was deeply dedicated to the control of nuclear weapons. He received two letters of commendation from project director Major General Leslie R. Groves, Jr. and a Presidential Certificate of Merit for work in the MIT Radiation Laboratory.