Advanced oxidation processes (AOPs) were initially proposed in the 1980s for drinking water treatment and have since been widely studied for treating various wastewaters. AOPs generate hydroxyl radicals (OH·) or sulfate radicals (SO4·-) to remove refractory organic matters, traceable organic contaminants, or certain inorganic pollutants, or to enhance biodegradability as a pre-treatment before biological treatment. This paper reviews the fundamental mechanisms of radical generation in different AOPs and discusses the treatment of landfill leachate and biologically treated municipal wastewater using various AOPs. The treatment efficiencies depend on the selected AOP type, physical and chemical properties of target pollutants, and operating conditions. Besides OH· or SO4·- oxidation, other mechanisms may occur during AOP treatment, contributing to pollutant removal. Recent advances in AOP treatment of landfill leachate and advanced oxidation of effluent organic matters (EfOM) in biologically treated secondary effluent (BTSE) for water reuse are highlighted.Advanced oxidation processes (AOPs) were initially proposed in the 1980s for drinking water treatment and have since been widely studied for treating various wastewaters. AOPs generate hydroxyl radicals (OH·) or sulfate radicals (SO4·-) to remove refractory organic matters, traceable organic contaminants, or certain inorganic pollutants, or to enhance biodegradability as a pre-treatment before biological treatment. This paper reviews the fundamental mechanisms of radical generation in different AOPs and discusses the treatment of landfill leachate and biologically treated municipal wastewater using various AOPs. The treatment efficiencies depend on the selected AOP type, physical and chemical properties of target pollutants, and operating conditions. Besides OH· or SO4·- oxidation, other mechanisms may occur during AOP treatment, contributing to pollutant removal. Recent advances in AOP treatment of landfill leachate and advanced oxidation of effluent organic matters (EfOM) in biologically treated secondary effluent (BTSE) for water reuse are highlighted.