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 on the philosophies of Bertrand Russell and Gottlob Frege.
Sainsbury taught for many years at King's College London, and became professor of philosophy at the University of Texas at Austin in 2002. He was editor of the leading philosophy journal Mind from 1990 to 2000. He was elected a Fellow of the British Academy in 1998.
- Bertrand Russell (Routledge, 1979) ("Arguments of the Philosophers" series)
- Paradoxes (Cambridge University Press, 1988)
- Reference Without Referents (Oxford University Press, 2005).
- Fiction and Fictionalism (Routledge, 2009).
- Seven Puzzles of Thought and How to Solve Them: An Originalist Theory of Concepts (with Michael Tye (philosopher)) (Oxford University Press, 2012).