This review paper provides an in-depth analysis of the photocatalytic activity of nanostructured metal oxides, including their photocatalytic mechanism, factors affecting photocatalytic efficiency, and methods to enhance photocatalytic performance through structural or material modifications. Nanostructured metal oxides, such as TiO₂, ZnO, and WO₃, are highlighted for their excellent photosensitivity, chemical stability, non-toxicity, and biocompatibility. The paper discusses the challenges and limitations of these materials, such as their reliance on UV light and rapid charge recombination, and explores strategies to overcome these issues, including doping, surface modification, heterojunction formation, and nanostructuring. Recent advancements in ZnO-based nanocomposites are also discussed, emphasizing their potential in environmental remediation, energy conversion, and biomedical applications. The review concludes by summarizing the applications of nanostructured metal oxide photocatalysts, including water purification, antimicrobial agents, air purification, and hydrogen production.This review paper provides an in-depth analysis of the photocatalytic activity of nanostructured metal oxides, including their photocatalytic mechanism, factors affecting photocatalytic efficiency, and methods to enhance photocatalytic performance through structural or material modifications. Nanostructured metal oxides, such as TiO₂, ZnO, and WO₃, are highlighted for their excellent photosensitivity, chemical stability, non-toxicity, and biocompatibility. The paper discusses the challenges and limitations of these materials, such as their reliance on UV light and rapid charge recombination, and explores strategies to overcome these issues, including doping, surface modification, heterojunction formation, and nanostructuring. Recent advancements in ZnO-based nanocomposites are also discussed, emphasizing their potential in environmental remediation, energy conversion, and biomedical applications. The review concludes by summarizing the applications of nanostructured metal oxide photocatalysts, including water purification, antimicrobial agents, air purification, and hydrogen production.