This is the first textbook to explore and explain the contribution of social groups and social identity to all aspects of sports and exercise — from leadership, motivation and communication to mental health, teamwork, and fan behaviour.In the context of increasing recognition of the importance of group processes for athletic performance, engagement in exercise and the business of sport, this book offers a new way of understanding, researching and practicing sport and exercise psychology Written by an international team of researchers at the cutting edge of efforts to apply social identity principles to the world of sport and exercise, this will be an essential resource for students, teachers and practitioners who are keen to be at the forefront of thinking and practice.