Abstract: Structures must be robust so that in case accidental damage occurs, they will not suffer damage disproportionate to the original cause. The awareness of the significance of structural robustness has intensified over the years. This article focuses on the concept and appraisal of structural robustness, as well as its role in risk mitigation for structures under accidental damage. Structural robustness is explained on the basis of energy principles. Further, a new quantitative measurement of structural robustness is developed, in which a dimensionless form of the energy absorption capacity of a structure satisfying the requirement of specific load-bearing capacity serves as a robustness index. A simply-supported beam is adopted to illustrate the use of the robustness index. Structural robustness plays a key role in risk mitigation. Several means of enhancing structural robustness are presented. Finally, the entire paper is summarized.