ABSTRACTSilica and silicon nanomaterials have diverse applications in the field of drug/gene delivery, lightweight aggregates, regenerative medicine, tissue engineering, cancer diagnosis/therapy, catalytic applications, and energy storage. There is an increasing demand for eco-friendly synthesis of silica and silicon nanomaterials with enough cost-effectiveness, safety, reliability, simplicity, scalability, and controllable particle size distribution features. These materials can be effectively obtained from various agrarian sustainable bio-resources, including rice husk ash, sugar-cane, coffee husk, wheat husk and corn cob ash. Using green and sustainable techniques can cause to eliminate or reduce laborious/complicated procedures and reduce the environmental contaminants to obtain advanced materials for high-tech applications. In this review, recent advancements pertaining to the catalytic and biomedical applications of silica and silicon nanoparticles are highlighted, as well as their greener synthetic methods.