Availability of affordable energy has enabled spectacular growth of industrialization and human development in all parts of the world. With growth now accelerating in developing countries, demands on energy sources and infrastructure are being stretched to new limits. Additional energy issues include the push for renewable resources with reduced greenhouse gas emissions and energy security affected by the uneven distribution of energy resources around the globe. Together, these issues present a field of opportunity for innovations to address energy challenges throughout the world and all along the energy flow. These energy challenges form the backdrop for this special expanded issue of MRS Bulletin on Harnessing Materials for Energy. This article introduces the global landscape of materials issues associated with energy. It examines the complex web of energy availability, production, storage, transmission, distribution, use, and efficiency. It focuses on the materials challenges that lie at the core of these areas and discusses how revolutionary concepts can address them. Cross-cutting topics are introduced and interrelationships between topics explored. Article topics are set in the context of the grand energy challenges that face the world into the middle of this century.