Water is a vital resource for all living organisms, yet only 2.5% of the Earth’s water is freshwater, with just 0.3% readily accessible. Increasing pollution from industrial waste, poor sewage treatment, and agricultural practices has exacerbated global water scarcity, making clean and safe water increasingly difficult to obtain. Conventional wastewater treatment techniques, including coagulation, ion-exchange, and membrane separation, are often inefficient, costly, and unable to completely eliminate contaminants such as heavy metals, toxins, and pathogens. Nanotechnology, with its ability to manipulate matter at the molecular level, offers innovative solutions for water purification. Nanomaterials, such as nanosorbents, nanomotors, nanophotocatalysts, and nanomembranes, have shown great promise in removing pollutants, including heavy metals, harmful microorganisms, and chemical toxins. These materials are highly efficient, offering large surface areas and rapid reaction rates, making them effective in decentralized water treatment. Despite their advantages, challenges such as high costs, potential health risks, and scalability remain barriers to widespread implementation. Continued research is needed to develop affordable and environmentally sustainable nanomaterials for large-scale applications. As nanotechnology advances, it holds great potential to address global water scarcity and pollution, contributing to a sustainable future and ensuring safe drinking water for all.