Access to clean and safe water is critical for human health and sustainable development, yet it remains a global challenge due to increasing industrialization, population growth, and pollution. Conventional treatment technologies often fail to remove emerging contaminants such as pharmaceuticals, endocrine disruptors, and resistant pathogens. Nanotechnology offers innovative, efficient, and versatile solutions for water purification through materials with unique properties at the nanoscale. This comprehensive review presents recent advances in nanotechnology-enabled water treatment, including nanomaterial types, purification mechanisms, performance data, challenges, and future perspectives.