Bondi, Hermann (1919-2005) was a British astronomer who formulated the steady-state theory of the origin of the universe with Fred Hoyle and Thomas Gold during the late 1940's. According to this theory, the universe had no beginning, will have no end, and continuously generates mass to keep its density steady as it constantly expands. Bondi and his colleagues later conceded in favor of the big bang theory, which deduces an explosive beginning of the universe.

After completing his early education in Vienna, Bondi earned undergraduate and graduate degrees in mathematics at Trinity College, Cambridge. He worked in the British Admiralty during World War II (1939-1945), and then taught mathematics at Cambridge University and at King's College, London. He also served as master of Churchill College, Cambridge, and played a major role in several important governmental space and energy agencies. In 1959, he was made a member of the Royal Society, and in 1973, he was knighted by Queen Elizabeth II.

In 1948, Bondi, Hoyle, and Gold put forth their cosmological theory of a steady-state universe, according to which the universe is the same everywhere and for all time. They assumed that matter is constantly being created from energy everywhere in the universe. Bondi described the major aspects of the theory in his 1952 book, Cosmology. The discovery of quasars, which showed that the universe had changed, and background radiation—a faint glow of radiation coming from all directions in space—later discredited the steady-state theory. Quasars indicated that the universe had changed since its beginning, and background radiation was considered evidence of an early hot state of the universe, which suggests that the universe had a specific origin in a violent explosion of dense, hot material.

Bondi died on September 10, 2005, in Cambridge, England.