This chapter aims to fill a gap in the legal literature by being the first dedicated exclusively to the burgeoning phenomenon of class actions in privacy law. Breach notification legislation, along with recent developments in privacy tort law in the United States and Canada, have contributed to an explosion in privacy class actions. Canada, for example, has seen more than 80 privacy class actions in the past 10 years distributed in logarithmic growth, compared to only 2 commenced before 2010. Privacy law protects the collection, processing, and dissemination of personal information, and violations at any of stages can give rise to class actions when formal requirements are met. Class proceedings are one of the foundational blocks of privacy class actions. Class actions in privacy law also face issues of multijurisdictional and cross-border claims. Many class actions in privacy law are extraterritorial by nature. The chapter also presents an overview of the key concepts discussed in this book.