This book presents a comprehensive overview of photocatalytic oxidation and its transformative role in addressing modern environmental challenges. It explores the fundamental mechanisms, synthesis strategies (including green routes), characterization tools, and applications in water, air, and soil remediation. Covering both well-established and emerging topics, such as carbon dioxide conversion, hydrogen peroxide synthesis, and the treatment of complex pollutants, the book combines theoretical insights with real-world applications. Special attention is given to sustainability, health impacts, scale-up constraints, and integration into modern environmental technologies. This book bridges fundamentals and applications across environmental, chemical, and materials science disciplines, offering a comprehensive perspective that integrates theory with practice. It provides unique coverage on the phytotoxicity and health risks of photocatalysts—an area often overlooked in technical books—while highlighting green synthesis and biobased carbon materials as promising next-generation strategies. In addition, it discusses scale-up limitations and photoreactor constraints, delivering practical insights into the challenges of industry implementation and guiding readers toward more sustainable and effective photocatalyst development.