The ideal structural material would be high strength and stiffness, with a tough ductile failure, all with a low density. Historically, no such material exists, and materials engineers have had to sacrifice a desired property during materials selection, with metals (high density), fibre composites (brittle failure), and polymers (low stiffness) having fundamental limitations on at least one front. The ongoing revolution of nanomaterials provides a potential route to build on the potential of fibre-reinforced composites, matching their strength while integrating toughening behaviours akin to metal deformations all while using low weight constituents. Here, the challenges, approaches, and recent developments of nanomaterials for structural applications are discussed, with an emphasis on improving toughening mechanisms – often the neglected factor in a field which chases strength and stiffness.