This book focuses on how rivalry influences fan perceptions and behaviors, the role of organizations to responsibly promote rivalries, and discusses how to decrease negative and group-member deviance surrounding sport rivalry. Rivalry is a phenomenon that helps organizations and participants increase their output while also engaging fans. The author argues that the goal of rivalry should be to increase engagement and interest in the product without stepping over a sometimes invisible line resulting in fan or group member negativity, deviance, and violence. Through the introduction of two scales that specifically measure how group members react to out-groups in the sport setting, this book offers scholars deeper insights into what rivalry means and how it can be used to responsibly promote the sport product.