Industrial effluent is a multifaceted environmental problem in terms of the presence of contaminants, such as heavy metals, organic chemicals, pharmaceuticals, and microorganisms. Traditional treatment schemes are not often effective for eliminating such contaminants. Nanotechnology, with its new and highly efficient nanomaterials, holds much hope. This chapter presents the basic principles of nanomaterials and their distinct characteristics like high surface area, reactivity, and adjustable functionality, which render them efficient agents in wastewater treatment. Different nanomaterials like metal oxides, carbon nanomaterials, and functionalized nanoparticles are presented along with their modes of action like adsorption, catalysis, and antimicrobial activity. The chapter also delves into the technical challenges involved in upscaling nanomaterial-based treatment systems, such as problems associated with synthesis, cost, regeneration, and environmental safety. The overview paves the way for more in-depth treatment of the topics in following chapters, highlighting nanotechnology's potential to transform sustainable industrial wastewater treatment.