Despite showing significant promises in the last few decades for the removal and cleaning of wastewater from manufacturing and town waste sources, photocatalysis has yet to make the leap from research in laboratories to real-world, large-scale applications. A significant portion of this cold progress can be attributed to the inherent physicochemical features of the majority of photocatalytic materials, which have a tendency to have poorer photoefficiency when exposed to visible light, in addition to a variety of engineering obstacles. Water treatment with photocatalysts is a sustainable solution to water contamination. Photocatalysis activates a semiconductor material with visible or UV light to break down organic, viral, and inorganic impurities in water. High efficiency, low energy usage, and sustainability are benefits of this technique. Photocatalysts work under sunlight, making them suitable for dispersed water filtration systems. This chapter reviews the history and activity of the photocatalyst in water purification. The chapter also discusses various types of photocatalysts along with its mechanism. The efficiency of these photocatalytic materials is something that is being more investigated, and thus, it is necessary to have a grasp of the function that these materials play in photocatalytic processes in order to handle the challenges that are associated with wastewater treatment.