A category of magnetic materials mostly composed of iron oxide (Fe2O3) is referred to as ferrites; the term ferrite originates from the Latin word for iron (Fe), “ferrum.” Ferrites are frequently encountered in the natural world, exhibiting a dark brown or gray hue, and possess a mechanical characteristic that is notably hard but fragile. Ferrite nanoparticles (FNMs) have drawn a lot of interest because of their numerous uses in a variety of fields, including wastewater treatment, electronics, magnetic, biomedicine, electrochemical water splitting, supercapacitor sensors, and biosensors. In this chapter, initially, the classification of ferrites on the basis of their crystal structure (spinel, hexagonal, garnet, and ortho) and magnetic field (soft and hard) was thoroughly explained. Furthermore, properties of FNMS especially magnetic properties, were briefly described. Consequently, various applications of ferrites, including water treatment, magnetic devices, corrosion protection, photocatalysis, biomedical, sensor and catalysis were discussed.