In most countries, sanitary landfill is nowadays the most common way to eliminate municipal solid wastes (MSWs). However, sanitary landfill generates large quantity of heavily polluted leachate, which can induce ecological risk and potential hazards towards public health and ecosystems. The application of advanced oxidation processes (AOPs) including ozone-based oxidation, Fenton oxidation, electrochemical oxidation, and other AOPs to treatment of landfill leachate was reviewed. The treatment efficiency in term of chemical oxygen demand (COD) of various AOPs was presented. Advantages and drawbacks of various AOPs were discussed. Among the AOPs reviewed, Fenton process should be the best choice, not only because it can achieve about 49~89% of COD removal with COD ranging from 837 to 8894？mg/L, but also because the process is cost-effective and simple in technological aspect, there is no mass transfer limitation (homogeneous nature) and both iron and hydrogen peroxide are nontoxic. 1. Introduction Due to rapid economic development in recent years, the excessive generation of municipal solid wastes (MSWs) has been identified as one of the most serious environmental problems in the world which needs to be addressed urgently for environmental protection. Up to 95% total MSW collected worldwide is disposed using the landfilling method [1]. After landfilling, solid waste undergoes a series of physicochemical and biological changes. Consequently, the degradation of the organic fraction of the wastes in combination with percolating rainwater leads to the generation of a highly contaminated liquid called “leachate”. Leachate may contain large amount of organic matter (biodegradable, but also refractory to be biodegraded), ammonia-nitrogen, heavy metals, and chlorinated organic compounds and inorganic salts. The characteristics of landfill leachate are affected by many factors, such as age, precipitation, weather variation, and waste types and compositions. In particular, the composition of landfill leachate varies greatly depending on the age of the landfill [2]. According to the landfill age, the leachate can be classified into three types: young, intermediate, and old, and the relationship of the characteristics of landfill leachate versus the age of landfill is summarized in Table 1 [3, 4]. The young landfill leachate is commonly characterized by high biochemical oxygen demand (BOD) (4000–13,000？mg/L) and chemical oxygen demand (COD) (30,000–60,000？mg/L), moderately high content of ammonium nitrogen (500–2000？mg/L), high ratio of BOD/COD (ranging from 0.4 to
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