In this work, the author focuses in particular on aggressive behavior in competitive sports (highly ranked professional, spectator, and Olympic sports) and on the behavior of fans accompanying sporting events. Aggression in sports, when considered from the point of view of the regulations in specific disciplines, has two main variants. The first variant is necessary aggression, which is both instrumental and non-instrumental and is potential in the sense that it allows the manifestation of emotions which are not outlined in the rules of the discipline. Thus, aggression is considered necessary when it results from the rules of a given sport. The second form of aggression is a non-instrumental and unpredictable aggression which is of an emotional origin. It is reactive, characterized by anger, and aims to cause harm. It is not stimulated by the rules of a given sport, but on the contrary is restricted and punished by the rules. The author also points out that the aggressive behavior of fans before, during, and outside a sporting event will never be necessary in this respect because the rules, guidelines, or specific regulations of a sport apply to the behavior of players, not fans. Therefore, their aggression is potential, emotional, planned, or spontaneous, but never necessary.