Mass political behavior is the study of how average citizens form and express opinions about politics and [Page 471]decide how to engage with the political system through voting or other forms of political participation. Political scientists interested in mass political behavior have drawn on a variety of disciplinary approaches to understand the topic, including history, economics, sociology, and more recently, psychology, biology, and neuroscience. Political psychologists interested in understanding mass political behavior have applied social psychological theories of attitudes, emotion, social cognition, and social identity to help improve our understanding of political behavior. This entry provides a brief overview of how psychology has been used to study public opinion, voting behavior, and political participation.