The widespread pollution of rivers, lakes, oceans and other water bodies by chemicals, plastics, heavy metals and oil spills, is causing major threats to human wellbeing and aquatic ecosystems. Continuous industrialization and urbanization, and the high population growth rates have aggravated water-related challenges in many countries. This trend indicates the limitations of existing treatment technologies in effectively removing aqueous pollutants. Nanomaterials with unique morphological, mechanical and physicochemical properties, have emerged as promising materials for wastewater remediation. Their outstanding features, including ultra-large surface area, excellent mechanical strength and customizable surface chemistry, have attracted significant research interests in recent years. This chapter covers the different types and classification methods of nanomaterials, including categorization, by dimension, chemical composition and origin. The synthesis techniques for nanomaterials, encompassing the top-down and bottom-up methods, are described in the chapter. It also describes the characterization of nanomaterials based on their physicochemical properties. Additionally, this chapter covers the various applications of nanomaterials in wastewater remediation.