John Francis Toland (born 28 April 1949, Derry) is an Irish mathematician based in the UK. He is currently Director of the Isaac Newton Institute for Mathematical Sciences and NM Rothschild & Sons Professor of Mathematical Sciences at the University of Cambridge, where he succeeded Sir David Wallace in October 2011.

His research interests include mathematical analysis and nonlinear partial differential equations, and he has made substantial contributions to the rigorous theory of steady water waves. In 1978, he proved Stokes' conjecture on the existence of gravity waves of maximum height on deep water, a previously open problem in mathematical hydrodynamics which dated back to the 19th century.He receive Sylvester Medal in 2014 for his original theorems and remarkable discoveries in nonlinear partial differential equations, including applications to water waves.