Confronting Water Insecurity provides an account of the role of multilateral cooperation and global institutions in transforming science, policy, and practice for water security from 1945 to 2024, a period characterized by significant disparities in water security between low- and high-income countries, ever-rising water use, and growing concerns about the harms of climate change and other disturbances on the global water cycle. Roberto L. Lenton tells how the scientific and policy response to these new challenges has become more global and integrated, and describes the role of global institutions in addressing fundamental global water issues with long-term implications for sustainability. Following the quest for water security as it transformed from an issue driven primarily by local or national interests into one of global concern, Lenton offers lessons from the successes and failures from 1945 to 2024 that will help us imagine the new approaches we need to ensure that the world can meet the next generation of water challenges. Beyond the world of water, he provides insights into how we can better address the global challenges that arise from humanity's complex relationships with the natural world.