Harold Alvin Fidler (August 2, 1910 – April 2, 2004) was the Associate Director of the Lawrence Radiation Laboratory from 1958 to 1974. During World War II he served as the Manhattan Project's California Area Engineer, where he worked with Ernest O. Lawrence's Berkeley Radiation Laboratory, which was developing calutrons for electromagnetic isotope separation. As such, he was responsible for the administration of contracts between the Army and the University of California.