The development of sustainable methodologies for the synthesis of functional nanomaterials has emerged as an important research direction toward reducing the environmental impact associated with conventional chemical and physical synthesis routes. This collection will focus on recent advances in green and sustainable approaches for the preparation of metallic, metal-oxide, magnetic, plasmonic, and hybrid nanomaterials, with particular emphasis on the use of biological resources, plant extracts, deep eutectic solvents, water-based systems, ultrasound-assisted processes, and other environmentally responsible methodologies. Contributions addressing synthesis mechanisms, reaction optimization, physicochemical characterization, reproducibility and structure–property relationships are particularly encouraged. The collection will also highlight emerging applications of sustainably synthesized nanomaterials in environmental remediation, water treatment, catalysis, sensing, energy, and biomedical technologies. By bringing together methodological advances and application-oriented research, this collection aims to provide a comprehensive perspective on how green synthesis can contribute to the development of next-generation functional nanomaterials