In the United States, the major forms are high school football, college football and professional football. Each of these three are played under slightly different rules. High school football is governed by the National Federation of State High School Associations, while college football by the National Collegiate Athletic Association and National Association of Intercollegiate Athletics. The major league for professional football is the National Football League (NFL). Other minor professional leagues also exist in the U.S., and may also have slightly different rules from those of the NFL.
The sport is also played in Europe, Japan, Mexico, and several other countries. The International Federation of American Football acts as an international governing body for the sport, but the organization has little standing in the United States.
American football is closely related to Canadian football but with some differences in rules and the field. Both sports can be traced to early versions of association football and rugby football.