The devastation and despair gripping Ukraine following the unprovoked invasion by neighboring Russia is heartbreaking and unthinkable. Such a loss of life and homeland has stirred wide concern around the world. This war sets back progress to establish a peaceful and sustainable world and to address important problems faced by all humanity, including climate change, environmental degradation, public health, and inequality. The international community of scientists cooperates extensively to address the challenges of our time, and a war that is destroying a stable and healthy nation and provoking a refugee crisis is no exception. What can the scientific community do most immediately to provide support and aid to its Ukrainian colleagues in their time of need? The community should focus on strengthening regional partnerships in Eastern Europe, networking to find refugees safe havens, speaking out forcefully against this invasion, and preparing to help rebuild Ukrainian science when the time is right.