The growing interest in sport as a field of research inquiry has been accompanied by an increased interest in the sports fan in his or her public role as a member of a spectator crowd. The expansion of spectator sport as a major leisure-time activity has produced changes in the ideology and practice of sport. This in turn has led to a variety of crowd phenomena that make the sports crowd an important subject in its own right. Here we examine the sports crowd as an aspect of collective behavior and discuss how the conduct of spectators before, during, and after a sports event can be affected by their belonging to a crowd. What is the relevance of the study of sports crowds? Why is the field important?