Robert Fox Bacher (August 31, 1905 – November 18, 2004) was an American nuclear physicist and one of the leaders of the Manhattan Project. Born in Loudonville, Ohio, Bacher obtained his undergraduate degree and doctorate from the University of Michigan, writing his 1930 doctoral thesis under the supervision of Samuel Goudsmit on the Zeeman effect of the hyperfine structure of atomic levels. After graduate work at the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT), he accepted a job at Columbia University. In 1935 he accepted an offer from Hans Bethe to work with him at Cornell University in Ithaca, New York. It was there that Bacher collaborated with Bethe on his book Nuclear Physics. A: Stationary States of Nuclei (1936), the first of three books that would become known as the "Bethe Bible".