Ferrites−the electro-ceramic materials have been considered highly important magnetic materials for more than half a century. The crystal structure of ferrimagnetic oxides falls into one of the following categories: spinel, magnetoplumbite(hexagonal), garnet, and orthoferrite. The development of spinel ferrite nanoparticles (SFNPs) has become more popular owing to their fascinating properties, such as their potential adsorption properties, superparamagnetic behavior, high stability, high value of resistivity, saturation magnetization, coercivity, low power losses, and ease of functionalization. These advantageous features make them suitable for use in various applications. This chapter aims to discuss the structure, general properties, and some recent applications of spinel ferrites. Commonly used synthesis techniques for nanocrystalline ferrites are discussed. The applications of nano-structured ferrites like antimicrobial activity, gas sensors, and dye degradation are discussed.