Water purification technologies are critical amidst global water scarcity and pollution. Magnetite (Fe3O4) nanoparticles (MNP) offer promising prospects for coagulation-based water treatment owing to their unique magnetic properties, substantial surface area, and customizable surface chemistry. This review presents a comprehensive overview of MNP synthesis, surface modification techniques, underlying mechanisms, and diverse applications in water purification via coagulation. We examine Fe3O4 nanoparticles' efficacy in removing contaminants such as heavy metals, organic pollutants (dyes), inorganic pollutants, microalgae, and pathogens from aqueous solutions. Furthermore, we discuss current challenges, recent advancements, and future opportunities in harnessing MNP for sustainable water purification technologies. This synthesis aims to provide researchers, engineers, and policymakers with a comprehensive understanding of the potential of MNPs in addressing critical global water quality challenges, emphasizing their role in advancing efficient and sustainable purification methodologies. © 2025 by SPC (Sami Publishing Company).