James Barber FRS FRSC MAE (16 July 1940 — 5 January 2020) was a British senior research investigator and emeritus Ernst Chain professor of biochemistry at Imperial College London, Visiting Professor at the Polytechnic University of Turin and Visiting Canon Professor to Nanyang Technological University (NTU) in Singapore.

Barber joined Imperial College in 1968, was made Reader in 1974, and was promoted to Full Professor in 1979.

Barber has published over 650 original research papers and reviews in the field of natural and artificial photosynthesis, editing 15 specialised books.

The focus of his research has been the investigation of photosynthesis and the functional role of the photosystems with emphasis on their structures.

Much of his work has focused on Photosystem II, a biological machine able to use light energy to split water into oxygen and reducing equivalents.