Donald A. Martin (born December 24, 1940), also known as Tony Martin, is an American set theorist and philosopher of mathematics at UCLA, where he is an emeritus professor of mathematics and philosophy.
Martin received his B.S. from the Massachusetts Institute of Technology in 1962 and was a Junior Fellow of the Harvard Society of Fellows in 1965–67. In 2014, he became a Fellow of the American Mathematical Society.
Among Martin's most notable works are the proofs of analytic determinacy (from the existence of a measurable cardinal), Borel determinacy (from ZFC alone), the proof (with John R. Steel) of projective determinacy (from suitable large cardinal axioms), and his work on Martin's axiom. The Martin measure on Turing degrees is also named after Martin.