The Big Bang theory was proposed by Georges Lemaître, a Belgian astronomer, cosmologist, and Catholic priest. In 1927, Lemaître formulated the modern Big Bang theory, suggesting that the universe began from a cataclysmic explosion of a small, primeval "super-atom" or "primeval atom"

. He proposed that the universe was expanding and that extrapolating backward in time implied it originated from an extremely dense and compact state. This idea marked the birth of Big Bang cosmology and was a radical departure from the scientific views of the time

. Lemaître's work integrated Albert Einstein’s theory of general relativity with astronomical observations, such as those by Edwin Hubble, who observed the expansion of the universe

. His hypothesis was initially called the "hypothesis of the primeval atom" and later became known as the Big Bang theory

. The term "Big Bang" itself was coined later by Fred Hoyle during a radio broadcast, though Hoyle favored a competing steady-state model

. In summary, Georges Lemaître is universally acknowledged as the originator of the Big Bang theory