Jeff McMahan (born 30 August 1954) is an American philosopher. He completed a BA degree in English literature at the University of the South (Sewanee), then did graduate work in philosophy in Britain as a Rhodes Scholar. He studied first under Jonathan Glover and Derek Parfit at the University of Oxford and was later supervised by Bernard Williams at the University of Cambridge, where he was a research fellow at St. John’s College. He has written extensively on normative and applied ethics. His publications include The Ethics of Killing: Problems at the Margins of Life (Oxford, 2002) and Killing in War (Oxford, 2009), which deals with Just War theory and argues against the deeply held beliefs within the theory, The Morality of Nationalism (co-edited with Robert McKim; Oxford, 1997), and Ethics and Humanity (co-edited with Ann Davis and Richard Keshen; Oxford, 2010).