Scour, the erosion of river and seabed sediments due to hydrodynamic forces, poses a significant threat to the integrity and longevity of hydraulic structures such as bridges, offshore platforms, and piers. The increasing prevalence of extreme scour events, driven by climate change and intensified flow conditions, necessitates the development of advanced, durable protection strategies. This chapter examines the use of nanomaterials as a novel and effective solution for mitigating extreme scour in fluvial and marine environments. Specifically, nanomaterials such as carbon nanotubes (CNTs), graphene oxide (GO), nanosilica (NS), nano-alumina (NA), nano MgO (NMg), and titanium dioxide are analyzed for their exceptional properties, including high mechanical strength, large surface area, and enhanced chemical stability, which can be harnessed to reinforce sediments and improve scour resistance. The chapter offers a comprehensive review of current research on the application of these nanomaterials in the development of erosion-resistant nanocomposites, protective coatings, and responsive materials with self-healing capabilities. Empirical studies and field trials demonstrating the efficacy of nanomaterials in reducing scour are discussed, alongside considerations of their environmental impacts, cost-effectiveness, and scalability for large-scale implementation. Additionally, the chapter highlights the potential synergies between nanomaterials and traditional scour protection techniques, offering a pathway toward more sustainable and resilient engineering solutions. Future research directions are also identified, focusing on optimizing the performance of nanomaterials in varied environmental conditions and addressing potential ecological concerns. Through this examination, the chapter contributes to the evolving field of hydraulic engineering, proposing nanotechnology as a transformative tool for addressing the challenges posed by extreme scour.