Functionalized magnetic nanomaterials (FMNs)Functionalized Magnetic Nanomaterials (FMNs) have acquired a lot of attention in the world of renewable energyEnergy due to their variety of applications and flexibility. These materials show great capability. This book chapter focuses on the synthesis and functionalizationFunctionalization of magnetic nanomaterialsMagnetic nanomaterials, their roles in catalysisCatalysis, supercapacitorsSupercapacitors, thermoelectric and piezoelectric devicesPiezoelectric devices, batteries, biofuels, and electrochemical sensorsElectrochemical sensors, along with some future potential applications. The magnetic propertiesMagnetic properties of FMNsFunctionalized Magnetic Nanomaterials (FMNs) assist with innovative approaches that contribute to advanced energy storageEnergy storage materials. FMNsFunctionalized Magnetic Nanomaterials (FMNs) not only enhance the performance of materials but also promote the development of a sustainable and eco-friendly environment, which is also cost-effective, thus providing a better alternative to the costly and toxic materials. This chapter focuses on various applications of FMNsFunctionalized Magnetic Nanomaterials (FMNs) and their future prospects in different fields.