Robert Leamon Bryant (born August 30, 1953) is an American mathematician. He works at Duke University and specializes in differential geometry.

Bryant grew up in a farming family in Harnett County and was a first-generation college student. He obtained a bachelor's degree at North Caroline State University at Raleigh in 1974 and a PhD at University of North Carolina at Chapel Hill in 1979. His thesis was entitled "Some Aspects of the Local and Global Theory of Pfaffian Systems" and was written under the supervision of Robert Gardner.

He worked at Rice University for seven years, as assistant professor (1979–1981), associate professor (1981–1982) and full professor (1982–1986). He then moved to Duke University, where he worked for twenty years as J. M. Kreps Professor.

Between 2007 and 2013 he worked as full professor at University of California, Berkeley, where he served as the director of the Mathematical Sciences Research Institute (MSRI). In 2013 he returned to Duke University as Phillip Griffiths Professor of Mathematics.

Bryant was awarded in 1982 a Sloan Research Fellowship. In 1986 he was invited speaker at the International Congress of Mathematicians in Berkeley.

He was elected in 2002 a fellow of the American Academy of Arts and Sciences, in 2007 a member of the National Academy of Sciences, in 2013 a fellow of the American Mathematical Society and in 2022 a fellow of the American Association for the Advancement of Science. He is also a member of the Association for Women in Mathematics, the National Association of Mathematicians and the Mathematical Association of America.

He served as the president of the American Mathematical Society for the 2-years term 2015–2016, for which he was the first openly gay president.

Bryant is on the board of directors of EDGE, a transition program for women entering graduate studies in the mathematical sciences. He is also a board member of Spectra, an association for LGBT mathematicians that he helped to create.