Sir Hermann Bondi (born 1 November 1919) is a British mathematician and cosmologist.
He was born in Vienna in Austria and studied at Trinity College, Cambridge. During World War II, and after being interned as an enemy alien, he worked with Fred Hoyle and Thomas Gold on radar. In 1948, Bondi, Hoyle and Gold formulated the steady-state theory.
He later taught mathematics, was director general of the European Space Research Organization , chief scientific adviser to the Ministry of Defence, chairman of the Natural Environment Research Council and master of Churchill College, Cambridge. He became a fellow of the Royal Society in 1959, a Knight Commander of the Bath in 1973, and received the Gold Medal of the Royal Astronomical Society in 2001.