The introductory chapter addresses the need for a new full-length manuscript on compulsory voting and discuss the meaning of the term. The chapter then reviews arguments for and against the requirement to vote, focusing mostly on matters of duty, collective action, legitimacy, representation, and the putative downstream consequences of compulsory voting. The chapter subsequently briefly reviews the history of compulsory voting and the potential reasons for its implementation. The chapter then provides data on where and how compulsory voting is used today and gives a detailed overview of recent events surrounding compulsory voting throughout the world. From there, the chapter discusses various empirical methods available to the scientific community for assessing the effects of the legal requirement to vote.