More is known about the factors that predict mental disorder than about the factors and processes that promote positive development among individuals exposed to atypically high levels of stress or adversity. In this brief Review of the science of resilience, we show that the concept is best understood as the process of multiple biological, psychological, social, and ecological systems interacting in ways that help individuals to regain, sustain, or improve their mental wellbeing when challenged by one or more risk factors. Studies in fields as diverse as genetics, psychology, political science, architecture, and human ecology are showing that resilience depends just as much on the culturally relevant resources available to stressed individuals in their social, built, and natural environments as it does on individual thoughts, feelings, and behaviours. With growing interest in resilience among mental health-care providers, there is a need to recognise the complex interactions across systems that predict which individuals will do well and to use this insight to advance mental health interventions.