The current trends in modern warfare and defence rely on nanoengineered multifunctional materials, which possess numerous characteristics, including futuristic stealth capabilities, adaptive stealth, multi-sensor functionality, low-energy-based sensing platforms, and lightweight and sustainable properties under harsh environmental conditions. Nanomaterials (1–100 nm scale) with their unusual physical and chemical properties offer new dimensions to defence and military-related strategic areas and industries. Nanomaterials have a wide range of applications in science and engineering, which are being widely used in the defence and industrial sectors. The nanomaterials are integrated in nearly all domains, e.g., nanoengineered armour composites for platforms and protection, nanomaterial-based chemical, biological, radiation, and nuclear (CBRN) sensors for efficient early detection and protection, next-generation ultralight energy materials and systems for power generation, nanomaterials-enabled adaptive camouflage, and even nano-enabled textiles for efficient thermal management. This chapter explores the diverse range of nanomaterials in defence technologies, with a focus on current trends and future technologies, including bio-inspired systems, metamaterials, and quantum materials, which are revolutionizing the military and defence sectors.