© 2015 Elsevier Ltd. All rights reserved. Reliable and cost-effective technologies for electrical energy storage are in great demand in sectors of the global economy ranging from portable devices, transportation, and sustainable production of electricity from intermittent sources. Among the various electrochemical energy storage options under consideration, rechargeable lithium-sulfur (Li-S) batteries remain the most promising platform for reversibly storing large amounts of electrical energy at moderate cost set by the inherent cell chemistry. The success of Li-S storage technology in living up to this promise calls for solutions to fundamental problems associated with the inherently low electrical conductivity of sulfur and sulfides, and the complex solution chemistry of lithiated sulfur compounds in commonly used electrolytes. These problems appear well posed for innovative solutions using nanomaterials and for fundamental answers guided by the tools of nanotechnology. Beginning with a review of the current understanding of Li-S battery chemistry and operation, this review discusses how advances in nano-characterization and theoretical studies of the Li-S system are helping advance the understanding of the Li-S battery. Factors that prevent Li-S cells from realizing the theoretical capacity set by their chemistry are discussed both in terms of the impressive advances in cell design enabled by nanomaterials and recent progress aimed at nanoengineering the cathode and other cell components. Perspectives and directions for future development of the Li-S storage platform are discussed based on accumulated knowledge from previous efforts in the field as well as from the accumulated experience of the writers of this review.