This chapter presents, further clarifies, and extends the foundations of economic resilience, with an eye to concerns of measurement. We examine the potential usefulness of theoretical concepts and empirical analyses in related fields such as ecology, management, regional science, and planning. We contend that there exists no single best approach to defining or measuring resilience across disciplines and that research should evolve to fit specific applications, though adhering to sound principles within each discipline. We illustrate the usefulness of our conceptual foundations in the design of an econometric analysis of economic resilience and summarize its application to survey data from two major disasters. In relation to the themes of this volume, economic resilience can serve to reduce entropy by countering the disarray in an economy in the aftermath of a disaster. At the microeconomic level, this also intersects with complexity in terms of synergies within an individual firm, and at the macroeconomic level manifests itself most notably through supply-chain interactions and network effects. In terms of spatial dynamics, it relates to geographic shifts in the location of economic activity by actual physical relocation of businesses, shifts of activity to branch plants, and the rebalancing of trade across regions.