The United Nations defines cities with populations of 10 million or more as megacities. Many of these megacities are rapidly expanding and require natural resources to sustain their growing populations and industries; many are also home to economic disparities. With these factors in mind, how are megacities distributing safe drinking water and sanitation and how is global climate change impacting water availability in these cities? In December 2015, UNESCO hosted a conference entitled "Water, Megacities, and Global Change" to address these and other questions. In this accompanying report, readers can learn about how fifteen cities - including Beijing, Chicago, Lagos, and Paris - are currently addressing water-related issues. In doing so, the report highlights both the unique challenges faced by these cities along with possible common solutions.