The discovery of nanomaterials in the past decades was described as one of the most exciting achievements in recent scientific and technological history due to the intriguing properties of materials in such small dimension. Since then, tremendous efforts were implemented to render significant advancements in synthesizing nanomaterials via versatile methods and utilizing as-prepared nanomaterials for diverse range of applications. In fact, nanomaterials were recognized as key element in many applications, including optoelectronics, batteries, and catalysis, and resulted in superior performance enhancement compared to their bulk counterparts. The spectacular advancements in energy conversion and storage in recent years were attributed to magnificent progress of characterization and application of nanomaterials. In this context, the surge of novel nanomaterials with appealing properties would greatly benefit the technological development towards sustainability and relief of dependence on traditional fossil fuels in our society. Therefore, this special issue would like to invite contributions in broad concepts of nanomaterials toward energy storage and conversion, including batteries, supercapacitors, fuel cells, solar cells, thermoelectrics, and catalysis.