Superoxide ion (O₂^•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O₂^•– is rather scarce. In addition, numerous studies on O₂^•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O₂^•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O₂^•– so as to enable researchers to venture into future research. It comprises the main characteristics of O₂^•– followed by generation methods. The reaction types of O₂^•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O₂^•– environmental chemistry is also discussed. The detection methods of O₂^•– are categorized and elaborated. Special attention is given to the feasibility of using ionic liquids as media for O₂^•–, addressing the latest progress of generation and applications. The effect of electrodes on the O₂^•– electrochemical generation is reviewed. Finally, some remarks and future perspectives are concluded.