John O'Keefe FRS FMedSci (born November 18, 1939) is an American-British neuroscientist, psychologist and a professor at University College London.
O'Keefe discovered place cells in the hippocampus, and that they show a specific kind of temporal coding in the form of theta phase precession. He shared the Nobel Prize in Physiology or Medicine in 2014, together with May-Britt Moser and Edvard Moser; he has received several other awards.