James B. Conant (1893-1978) was an American chemist and government official.
He worked closely with Vannevar Bush to spur the U.S. government to develop an atomic bomb, serving as Chairman of the National Defense Research Committee to mobilize science for the war effort. He was Bush's alternate on the Military Policy Committee and served as one of General Groves' advisers on scientific matters. He witnessed the Trinity test and was on the Interim Committee that made recommendations on using the atomic bombs against Japan.
Conant served as president of Harvard from 1933-1953. He also served as the first U.S. Ambassador to West Germany from 1955-1957.
During World War I he served in the U.S. Army developing poisonous gases (for more information, see historian Alex Wellerstein's article, "Conant's War: Inside the Mouse-Trap"). He visited Germany in 1925, touring the major universities and laboratories and meeting with leading German chemists. Conant returned to teach at Harvard, and eventually became president, reforming many of Harvard’s previous policies.