Petroleum refinery processes generate large quantities of wastewater, containing various harmful and toxic organic compounds. These pollution poses a significant threat to water resources as inadequate measures are taken to protect the environment from its harmful effects. Petroleum wastewater is recalcitrant substances that are hardly degraded by conventional methods such as biological and membrane processes. Advanced oxidation processes are the best solution for treating petroleum refinery wastewater due to the co-existence of hydroxyl radicals, which act as powerful oxidizing agents. They have the potential to efficiently treat various toxic, organic pollutants and complete degradation of contaminants (mineralization) of emerging concern. This chapter explores the performance of photocatalysis oxidation methods for the treatment of petroleum refinery wastewater.