Water is an integral component of climate change and the primary medium through which it exhibits its impacts. With the world facing growing water challenges in many regions, how climate change will affect future societies cannot be understood without looking at its impact on this most vital of our planet’s resources. This World Water Assessment Programme Special Report brings together messages on water and climate change from the World Water Development Report 3: Water in a Changing World. A joint effort of the 26 United Nations agencies that make up UN-Water, the triennial World Water Development Report is the United Nations’ foremost and most comprehensive review of the state of the world’s freshwater resources. Water in a Changing World shows that changes in our water resources are shaped to a great extent by a number of key externalities, among them climate change, and that decisions taken far from the conventionally defined water sector have a tremendous influence on water resources and how they are used or misused. These two principle messages of the report could not be timelier, with the challenges of climate change currently being squarely addressed and innovative responses sought with such enthusiasm. Water in a Changing World describes the dynamic linkages that interconnect changes in climate, the state of our water resources, demographic expansion and migration issues, food and energy shortages, and the continuing challenge of poverty. Rather than addressing these issues in isolation, it argues that a holistic approach is crucial if we are to solve the crises we face today and avoid worse crises tomorrow.