Denis Weaire has made significant contributions to solid state theory, materials science and computational physics. His early work on pseudopotential theory provided lasting insights into the factors which determine the structure of metals. He laid many of the foundations of the theory of amorphous tetrahedrally bonded semiconductors, beginning with a remarkable proof of the existence of a band gap for the Weaire–Thorpe Hamiltonian. Other achievements include the first simulations of structure, coarsening and rheology of a realistic two-dimensional foam, and the incorporation of Plateau borders. The computation of a three-dimensional structure (the Weaire–Phelan structure) which has cells of equal volume and a surface area less than that of Kelvin’s 1887 tetrakaidecahedra was hailed as a significant discovery for minimal surface theory as well as foam experiments. Observations of new solitary wave phenomena in foam drainage and the formulation of a corresponding theory, lend further impetus to rapid progress in this field.