Yihong Du is internationally renowned for his contributions to the theory of nonlinear elliptic and parabolic partial differential equations and their application in chemical reaction theory and population dynamics. He is a pioneer and leader in the use of nonlinear free boundary problems to model spreading phenomena and has resolved long standing problems on sharp thresholds, boundary blow up, bifurcation and multiplicity. His papers have been highly influential. He has also made significant contributions to the advancement of science through mentoring, conference organisation and service on committees and panels.