As the global energy crisis intensifies, the pursuit of clean and renewable energy sources has become critical. Hydrogen, recognized as a sustainable and eco-friendly energy carrier, is emerging as a key solution for future energy needs, with water splitting being a promising approach for its large-scale production. This chapter provides a comprehensive analysis of how nanomaterials contribute to improving the efficiency of water splitting for hydrogen generation. It begins by addressing the global energy crisis and highlighting the significance of hydrogen as a clean energy source. The discussion then covers the fundamental concepts of water splitting, focusing on photocatalytic and electrocatalytic techniques. Various nanomaterials, including metal oxides, nitrides, sulfides, and carbon-based structures, are examined for their catalytic capabilities. Special attention is given to how their nanoscale properties enhance surface area, charge separation, and overall catalytic performance. The chapter also details the underlying mechanisms of hydrogen generation facilitated by nanomaterials, as well as current challenges—such as material stability and scalability—that need to be addressed to optimize performance. Finally, we discuss future directions for research and practical applications of nanomaterials in hydrogen production, providing insights into their potential to revolutionize the clean energy sector.