This article reviews the synthesis, characterization, and applications of iron oxide nanoparticles (NPs). Iron oxide NPs, known for their unique properties such as superparamagnetism, surface-to-volume ratio, and ease of separation, have gained significant attention due to their potential in various fields including biomedicine, agriculture, and environmental applications. The review covers various physical, chemical, and biological methods for synthesizing these NPs, focusing on size and morphology control, magnetic properties, and surface modifications. Surface coatings with organic or inorganic molecules are crucial for enhancing biocompatibility and stability. The article also discusses the challenges and future directions in the field, emphasizing the importance of understanding the interaction mechanisms between NPs and biological systems. Key techniques for synthesis, such as wet chemical, dry processes, and microbiological methods, are compared, and the impact of these methods on NP properties is highlighted. Additionally, the article explores the potential of iron oxide NPs in medical treatments, industrial production, and diverse materials, including cosmetics and clothing. The review concludes by discussing the factors that enhance the efficiency of iron oxide NPs, such as cost-effectiveness, size, shape, and magnetic susceptibility, and the need for tailored surface chemistry for specific biomedical applications.This article reviews the synthesis, characterization, and applications of iron oxide nanoparticles (NPs). Iron oxide NPs, known for their unique properties such as superparamagnetism, surface-to-volume ratio, and ease of separation, have gained significant attention due to their potential in various fields including biomedicine, agriculture, and environmental applications. The review covers various physical, chemical, and biological methods for synthesizing these NPs, focusing on size and morphology control, magnetic properties, and surface modifications. Surface coatings with organic or inorganic molecules are crucial for enhancing biocompatibility and stability. The article also discusses the challenges and future directions in the field, emphasizing the importance of understanding the interaction mechanisms between NPs and biological systems. Key techniques for synthesis, such as wet chemical, dry processes, and microbiological methods, are compared, and the impact of these methods on NP properties is highlighted. Additionally, the article explores the potential of iron oxide NPs in medical treatments, industrial production, and diverse materials, including cosmetics and clothing. The review concludes by discussing the factors that enhance the efficiency of iron oxide NPs, such as cost-effectiveness, size, shape, and magnetic susceptibility, and the need for tailored surface chemistry for specific biomedical applications.