Our world is at a critical moment. May 30th saw the highest daily figure recorded worldwide for new cases of COVID-19, with countries on every continent attempting to stop the transmission of the virus and save lives. In this letter to world leaders, more than 230 former world leaders and leading global health experts and economists underline the urgency of addressing the medical emergency and providing debt relief to the poorest countries and more resources to the international financial institutions delivering immediate relief to countries facing the effects of an unprecedented, global crisis.