Water contamination is a critical global health issue, and ensuring access to clean drinking water through affordable and efficient technologies is vital for sustainable economic development. Nanotechnology has emerged as a transformative tool in water quality control and wastewater treatment, offering innovative solutions for pollutant removal. Nanoscale materials, with their exceptional adsorption characteristics, enhanced photocatalytic activity, and high reactivity, have been extensively studied in pilot-scale, laboratory, and in situ applications, showing remarkable potential in improving water treatment processes. This chapter examines the impact of nanotechnology on water quality control and wastewater treatment, focusing on advanced nanomaterials such as carbon nanotubes, graphene, metal nanoparticles (e.g., iron, magnesium zinc, and silver), as well as magnetic-core composites including cobalt, nickel, and iron, metal and, oxide nanoparticles. These materials are compared with conventional treatment methods with respect to cost-efficiency and capability for the removal of organic and inorganic pollutants. Furthermore, this review addresses the challenges, limitations, and future perspectives of employing engineered nanomaterials in the treatment of wastewater and drinking water, highlighting their potential to revolutionize global water quality management.