British mathematician and cosmologist who, with Fred Hoyle (Hoyle, Sir Fred) and Thomas Gold (Gold, Thomas), formulated the steady-state theory of the universe.

Bondi received an M.A. from Trinity College, Cambridge. During World War II he worked in the British Admiralty (1942–45). He then taught mathematics at Cambridge (1945–54) and at King's College in London (1954–85; emeritus 1985); he served as master of Churchill College, Cambridge, from 1983 to 1990. Bondi combined his academic career with active involvement in public service. He was director general of the European Space Research Organization (1967–71), chief scientific adviser to the British ministry of defense (1971–77), chief scientist of the department of energy (1977–80), and chairman of the Natural Environment Research Council (1980–84).

In 1948 Bondi, Hoyle, and Gold advanced their cosmological theory of a steady-state universe (steady-state theory), which postulates that the universe is the same everywhere and for all time. This means that as the universe expands, new matter would have to be created to balance this expansion. The theory of an eternal, steady-state universe, with no specific origin, has fallen into disrepute since the discovery (1961) of cosmic background radiation (i.e., a faint glow of radio radiation emanating from all directions in space), which strongly suggests that the universe began at some definable moment in the past with a violent explosion of an extremely dense and intensely hot mass of material.

Works by Bondi include Cosmology (1952; reissued 1960), The Universe at Large (1960), Relativity and Commonsense (1964), and Assumption and Myth in Physical Theory (1967). He was made a fellow of the Royal Society in 1959 and was knighted in 1973. His autobiography, Science, Churchill, and Me, was published in 1990.