The 2020 edition of the United Nations World Water Development Report (WWDR) addresses the critical linkages between water and climate change in the context of the broader sustainable development agenda. The report is not meant to be a purely technical examination of the impacts of climate change on the hydrological cycle. Rather, the report focuses on the challenges, opportunities and potential responses to climate change – in terms of adaptation, mitigation and improved resilience – that can be addressed through improving how water resources are management and used, while providing water supply and sanitation services for all in a sustainable manner. In doing so, the report tackles two of the most critical crises the world will continue facing over the next several decades: Water (in)security and climate change.