William George Penney, Baron Penney OM, KBE PhD, DSc,, FRS, FRSE, FIC, Hon FCGI (24 June 1909 – 3 March 1991), was an English mathematician and professor of mathematical physics at the Imperial College London and later the rector of Imperial College. He is acknowledged as having a leading and integral role in the development of Britain's nuclear programme, a clandestine programme started in 1942 during World War II which produced the first British atomic bomb in 1952.