**Abstract**

The exploration of functional nanomaterials with superior catalytic activity for practical photocatalytic water decontamination is of significant importance. Perovskite-based nanomaterials, which demonstrate excellent photophysical and catalytic properties, are widely investigated as a class of adaptable materials for the photocatalytic degradation of environmental pollutants. This chapter introduces the recent progresses in using perovskite-based nanocomposites with particular emphasis on the applications for effective photocatalytic degradation of organic pollutants in wastewater. It starts by presenting the general principles and mechanisms governing photocatalytic degradation of organic pollutants in water by perovskite, along with the design criteria for perovskite-based nanocomposites. It then explains various strategies used to prepare perovskite-based nanocomposites with the aim of enhancing their photocatalytic activity. By the end of the chapter, the remaining challenges and perspectives for developing efficient perovskite-based photocatalysts with potential large-scale application are highlighted.

**Keywords:** perovskite, photocatalysis, water decontamination, reactive oxidation species, nanomaterials, nanocomposites
