This chapter presents a forward-looking evaluation of emerging nanomaterials and technologies that are shaping the future of water and wastewater treatment. It highlights recent innovations across key classes of materials—including metal oxide, silver, iron, carbon-based, and cellulose nanomaterials—and examines their evolving roles in adsorption, photocatalysis, sensing, and contaminant removal. Special emphasis is placed on sustainable synthesis strategies, environmental safety considerations, and the performance metrics required for real-world implementation. This chapter further explores the growing integration of nanomaterials into advanced treatment systems such as membrane-assisted processes and nanobioremediation, outlining how these hybrid approaches enhance efficiency and selectivity. Emerging research directions in photocatalysts and adsorbents are analyzed, including multifunctional nanostructures, heterojunction engineering, and system-level scalability. A review of notable progress over the past decade highlights technological breakthroughs and persistent challenges, providing a grounded framework for future opportunities in nanomaterial design, environmental compatibility, and large-scale application. This chapter concludes with strategic perspectives on next-generation water treatment technologies aligned with the author’s research expertise.