The increasing global demand for clean water, exacerbated by population growth, industrialization, and climate change, has made desalination and brackish water treatment essential. Traditional desalination techniques, such as reverse osmosis (RO) and forward osmosis (FO), have been widely used, but both face challenges, including high energy consumption and membrane fouling. Nanotechnology offers promising advancements to overcome these limitations. Nanomaterials such as carbon nanotubes (CNTs), graphene, metal-organic frameworks (MOFs), and covalent organic frameworks (COFs) have been extensively explored to improve water desalination and brackish water treatment. In RO, nanomaterials enhance membrane performance by improving water permeability, salt rejection, and fouling resistance. In FO, nanomaterials are used both as membrane additives and draw solutes to increase efficiency while minimizing energy consumption. Despite significant progress, areas for improvement remain, particularly in addressing the cost of nanomaterial production, scaling up applications, and ensuring long-term membrane durability. This study focuses on the integration of nanotechnology into desalination processes, highlighting the contributions of nanomaterials in membrane technology and identifying future research needs. Nanomaterials have the potential to revolutionize water treatment by making it more energy-efficient, cost-effective, and sustainable, but further advancements are necessary to fully realize these benefits.