Ellis is professor emeritus of applied mathematics, University of Cape Town, South Africa. An astronomer and expert in tetrad methods to study cosmological dynamics and Bianchi Universes, he enunciated the dynamical systems approach to cosmology and nonlinear dynamics of cosmic microwave background anisotropies. He has written on the philosophy of cosmology, in particular the multiverse idea. He now works on complexity theory and the nature of the brain. He is a fellow (former president) of the Royal Society of South Africa, Royal Astronomical Society, Academy of Science of South Africa (ASSAf), and Royal Society (London). He is former president of the Intl. Society of General Relativity and Gravitation. He has won: Star of South Africa Medal; Gold Medal, ASSAf; Natl. Science and Technology Forum Lifetime Award; and Templeton Prize. He is a founding member, Inter Academy Council.