Ilya, Viscount Prigogine (Russian: Илья Романович Пригожин) (25 January 1917, Moscow – 28 May 2003) was a Russian-born Belgian chemist and Nobel Laureate chemist noted for his work on dissipative structures, complex systems, and irreversibility. He won the Nobel Prize in Chemistry in 1977.

In his 1997 book, The End of Certainty, Prigogine contends that determinism is no longer a viable scientific belief. "The more we know about our universe, the more difficult it becomes to believe in determinism." This is a major departure from the approach of Newton, Einstein and Schrödinger, all of whom expressed their theories in terms of deterministic equations.