In the era of extreme industrialization, pollution degradation is the biggest issue faced by the world because of its negative impacts on all living beings and the environment. Photocatalysis is one of the most favorable AOPs for pollutant degradation owing to its properties such as simplicity, reproducibility, environmental friendliness, non-toxicity, and technological and economical sustainability. This chapter explains what a photocatalyst is, the process of photocatalytic pollutant degradation, photocatalyst heterostructure modifications, and their application in various pollutant degradation activities like dye degradation, drug degradation, antimicrobial activity, and heavy metal removal.