Agriculture plays an essential role in sustaining society, yet the substantial waste produced during agricultural processes presents a major challenge for waste management. Often, agricultural waste is simply burned, posing environmental concerns. To address these issues, the revalorisation of agricultural waste by converting it into high-value nanomaterials offers a promising approach. This work reviews recent advances in the synthesis of nanomaterials from agricultural waste, focusing on materials such as carbonaceous compounds, metal-organic frameworks (MOFs), polymers, and silica-based nanomaterials. It also explores their applications in key sectors, including agriculture, water treatment, and medicine. A feasibility analysis assessed both economic viability and environmental impact, demonstrating that polymeric, carbon-based, and siliceous nanomaterials are particularly cost-effective and environmentally beneficial. This revalorization process not only generates commercially valuable nanomaterials but also promotes sustainable waste management practices. The study underscores the significant potential of agricultural waste as a resource for producing nanomaterials, aligning with both waste reduction and the generation of marketable products.