R. Mark Sainsbury (born 1943) is a philosopher from the United Kingdom who has worked in the areas of philosophical logic, philosophy of language, and the philosophies of Bertrand Russell and Gottlob Frege.
Sainsbury taught for many years at King's College London[1], and became professor of philosophy at the University of Texas at Austin in 2002.[2] (He still teaches in the summer months in London.) He was editor of the leading philosophy journal Mind from 1990 to 2000. He is also a Fellow of the British Academy.
His first book was on Bertrand Russell (Routledge, 1979). His most recent book, Fiction and Fictionalism (Routledge, 2009) concerns the semantic and ontological status of fictions. Reference Without Referents (Oxford, 2005), is on the semantics of referring expressions. His book Departing From Frege (2002) is on the philosophy of Gottlob Frege. He has also written about paradoxes (Paradoxes Cambridge, 1988, 1995, and Tolerating Vagueness, published in the Proceedings of the Aristotelian Society, 1989-9).