The papers selected for publication in the Special Issue "Urban and industrial wastewater disinfection and decontamination by Advanced Oxidation Processes (AOPs): current issues and future trends" and published in this book, include topics related with (waste)water treatment and its reuse, disinfection, and pollutant degradation, advancing the know-how of the topics or assessing their integration into the new age of the circular economy of water. Likewise, aspects such as modeling of degradation processes and new materials synthesis were published, aiming to improve, optimize and predict the efficacy of the existing or the novel treatment processes. Moreover, pilot plant operation and large-scale processes were featured, assessing the feasibility of these new treatment methods in real world applications. Overall, the Special Issue and this book present innovative solutions on the field of water and wastewater treatment, with a view on the future technologies that will form the next advances of the field.