DOE’s 2015 Energy-Water Nexus Roundtable Series engaged stakeholders from industry, academia, utilities, state and local governments, National Laboratories, and other federal agencies in focused discussions about the energy-water nexus. These six roundtable discussions1 brought up a number of challenges and opportunities in DOE’s mission space in the areas of fuels, water infrastructure, electricity, and systems integration. This document includes (1) top-level takeaways from the entire roundtable series that cut across science, technology, and policy and (2) topical summaries of discussions from all six roundtables in the series.