Christopher Isham is a theoretical physicist at Imperial College London. where he is a Distinguished Research Fellow of the Faculty of Natural Sciences, in the Department of Physics

His main research interests are quantum gravity and foundational studies in quantum theory. He was the inventor of an approach to temporal quantum logic called the HPO formalism, and has worked on loop quantum gravity and quantum geometrodynamics. Together with John Baez, Isham is known as a proponent of the utility of category theory in theoretical physics. In recent years, he has been working on a new approach to quantum theory based on topos theory. Isham has appeared in several NOVA television programmes as well as a film about Stephen Hawking. Physicist Paul Davies has described Isham as "Britain's greatest quantum gravity expert." As a practicing Christian, Isham has also written about the relationships among philosophy, theology, and physics. He has received the Dirac Medal for his works on quantum gravity.