The improper treatment of wastewater has cost humanity a large amount of access to clean water. Treating wastewater, by definition, means to remove pollutants, either physically or chemically. A chemical method of treating wastewater, the Fenton process, was deemed useful for the job. It includes a solution-based reaction that produces radicals to oxidize and break pollutants down. Variations of the Fenton process, each with their unique method, have been developed to increase the process’s efficacy and efficiency further. Admittedly, however, the information on this subject is relatively few, when compared to other more recent methods of treatment. This paper aims to present and discuss a wide variety of information on the Fenton process and its derivatives, including Electro-Fenton, Sono-Fenton, and Photo-Fenton among others.