Magnetic iron oxide nanomaterials (MIONs) have been extensively investigated for the various important applications. Coprecipitation, hydrothermal, high temperature decomposition of organic precursors, microemulsions, polyol methods, electrochemical methods, aerosol method, sonolysis and green synthesis processes for the fabrication of MIONs have been reviewed. Different characterization methods like XRD, SEM, EDX and TEM for the as prepared MION materials have been studied. Important applications of MIONs in the field of biomedical, nanorobotics and energy devices have also been addressed in this review. Target oriented drug delivery and hyperthermia applications of MIONs have also focused