Resilience in this chapter is defined as the ability of a socio-technical system to sustain or quickly recover its services to society even under the condition of major stress. Resilience includes a preventive aspect (sustain service functionality) as well as a crisis-management aspect (recover quickly). It may be used to characterize a system (descriptive), but it may also serve as a normative concept to improve a system towards a more resilient stage, such as building back better. It includes technical design criteria as well as organizational and institutional performance. Finally, resilience implies a dynamic approach based on social and institutional learning The paper distinguishes four different modes of resilience: (i) building back better; (ii) adaptive; (iii) transformative and (iv) biomimetic. Based on complexity theory, the paper advocates a dynamic, comprehensive and transformative perspective when analysing or designing energy systems.