John O'Keefe (born 18 November 1939) is an American-British neuroscientist and a professor at the Sainsbury Wellcome Centre for Neural Circuits and Behaviour and the Research Department of Cell and Developmental Biology at University College London. He is known for his discovery of place cells in the hippocampus and his discovery that they show a specific kind of temporal coding in the form of theta phase precession.He received Louisa Gross Horwitz Prize in 2013.