Energetic materials are the reactive materials containing fuels and oxidizers that can liberate chemical energy preserved in their molecular structure. Nano-energetic materials have found to be the potential sources for extremely high heat release rates, tailored burning rate, extraordinary combustion efficiency, and reduced sensitivity. These materials play a vital role in defense applications as a recent advancement in emerging areas such as manufacturing of explosives, solid and liquid propellants, rocket propelling, advanced gun propellant materials. Considering the immense scope of these functional materials, this chapter focuses to cover the fundamental aspect of energetic materials, description of contemporary reported literature on design and synthesis of nano-energetic materials and their significance for microscale applications in the defense sector. © 2019, Springer Nature Singapore Pte Ltd.