In the pursuit of sustainable and environmentally conscious chemical synthesis, the integration of photo-redox catalysts has emerged as a promising strategy. This book chapter explores the transformative potential of photo-redox catalysts in greener synthetic methodologies. Highlighting the principles and applications of photo-redox catalysis, this chapter delivers the key mechanism that underlines these processes, elucidating how light can be harnessed to drive challenging chemical transformation with high efficiency and selectivity. Throughout this chapter, various case studies and examples illustrate the versatility of photo-redox catalysis across a range of synthetic contexts, including organic synthesis, medicinal chemistry, and material science. In conclusion, the prospects of a greener synthetic approach are discussed, besides its potential for further development and application in the synthesis of a broad range of organic molecules and photo-luminescence hybrid materials.