George Francis Rayner Ellis is the Emeritus Distinguished Professor of Complex Systems in the Department of Mathematics and Applied Mathematics at the University of Cape Town in South Africa.

He co-authored The Large Scale Structure of Space-Time with University of Cambridge physicist Stephen Hawking, published in 1973, and is considered one of the world's leading theorists in cosmology. He is an active Quaker and in 2004 he won the Templeton Prize.

From 1989 to 1992 he served as President of the International Society on General Relativity and Gravitation. He is a past President of the International Society for Science and Religion. He is an A-rated researcher with the NRF.

Ellis attended the University of Cape Town, where he graduated with honors with a Bachelor of Science degree in physics with distinction. He received a PhD in applied mathematics and theoretical physics at Cambridge University.