Resilience is the ability to avoid, minimise, withstand, and recover from the effects of adversity, whether natural or man-made, under all circumstances of use. Energy resilience is the ability of the energy system to provide and maintain an acceptable level of service in the face of various challenges to normal operation. Loss of resilience can cause loss of valuable energy system services, and may even lead to rapid transitions or shifts into qualitatively different situations and configurations. The resilience of energy systems is defined as the capacity of an energy system to withstand perturbations from climatic, economic, technological and social causes and to rebuild and renew itself afterwards. This book describes the resilience of energy systems.