The COVID-19 pandemic represents a health system shock of unprecedented scale. Health systems resilience – defined as the ability to absorb, adapt and transform to cope with shocks – is needed to ensure sustained performance of the health system functions (governance, financing, resource generation and service delivery) so that the ultimate health system goals, especially that of improving the health of the population, can be achieved. As we have witnessed, few countries could achieve this goal and even fewer could do so in a sustained way – leaving all countries with important lessons to learn. The lessons derived in this study can inform both the ongoing efforts while countries are still grappling with the pandemic, as well as help ensure these efforts also incorporate a longer-term perspective, thus improving preparedness to any future health system shocks. While there is no ‘one-size-fits-all’ response that all countries could replicate, the study identifies 20 key strategies, grouped according to the health system functions, that have been found as enhancing health systems resilience in the face of COVID-19. They have strong interlinkages and do not work in isolation, and this book also considers how the health system operates in the context of other systems, and broader political and governance structures. The strategies describe how to secure and (re)allocate financing while leaving no one behind. They emphasize the need for more health workers who are fit for the job and are well supported. They demonstrate the importance of strong public health systems and safety nets. They show how providers surged capacity and adapted care pathways for both COVID-19 and non-COVID-19 patients. While the relative importance of the various strategies and their configurations will depend on the specific country contexts, governance emerges as the foundation and lever for health system functioning and resilience. It plays a crucial role in enabling all other functions to work in unison to ensure adequately financed and otherwise well-resourced health service delivery to promote improved health. This study is targeted at policy-makers and has two aims. First, it provides national policy-makers with evidence from other countries to assess their own responses to COVID-19 and incorporate adjustments that are appropriate for their national contexts. To this end the study offers examples of assessment areas for each of the identified strategies that can be used as the first step in national assessments of health systems resilience. Second, the findings and lessons contained in the study enable us to draw experience from the COVID-19 pandemic to begin ‘building back better’ to improve the response to future health system shocks and hopefully even pre-empt them. This supports the transition from managing the crisis to achieving more resilient health systems and societies.