The National Football League (NFL) is the largest professional American football league. It is an unincorporated 501(c)(6) association controlled by its members. It was formed by eleven teams in 1920 as the American Professional Football Association (the league changed the name to American Professional Football League in 1921 and then settled on its current name in 1922). The league currently consists of thirty-two teams from American cities and regions, divided evenly into two conferences — the American Football Conference (AFC) and National Football Conference (NFC) — of four four-team divisions.

The regular season is a seventeen-week schedule during which each team has one bye week and plays sixteen games. This schedule includes six games against a team's divisional rivals, as well as several inter-division and inter-conference games. The season currently starts on the Thursday night in the first full week of September (the Thursday after Labor Day) and runs weekly to late December or early January.

At the end of each regular season, six teams from each conference play in the NFL playoffs, a twelve-team single-elimination tournament that culminates with the championship game, known as the Super Bowl. This game is held at a pre-selected site which is usually a city that hosts an NFL team. The following week, selected all-star players from both the AFC and NFC meet in the Pro Bowl, held in Honolulu, Hawaii.

While baseball is known as America's "national pastime," football is the most popular sport in the United States. According to the Harris Poll, professional football moved ahead of baseball as the fans' favorite in 1965 and has remained America's favorite sport ever since. In a Harris sports poll done in 2008, the NFL was the favorite sport of nearly as many people (30 percent) as the combined total of the next four professional sports – baseball (fifteen percent), auto racing (ten percent), hockey (five percent) and men's pro basketball (four percent), Additionally, Football's American TV viewership ratings now surpass those of other sports.

The NFL has the highest per-game attendance of any domestic professional sports league in the world, drawing over 67,000 spectators per game for each of its two most recently completed seasons, 2006 and 2007. However, the NFL's overall attendance is only approximately 20% of that of Major League Baseball, due to MLB's much longer schedule (about 162+ games).

see: History of American football The National Football League is a loose coalition of technically independent football teams from across the state of Ohio that had existed in some form since the 1890s. An unofficial "championship" was contested since 1903. "League" powerhouses included the Canton Bulldogs, Ironton Tanks and the Massillon Tigers.

The American Professional Football Association was founded in 1920 at a Hupmobile dealership in Canton, Ohio. The eleven founding teams initially struck an agreement over player poaching and the declaration of an end-of-season champion. Legendary athlete Jim Thorpe of the Canton Bulldogs was elected president. Only four of the founding teams finished the 1920 schedule and the undefeated Akron Pros claimed the first championship. Membership of the league increased to 22 teams in 1921, but throughout the 1920s the membership was unstable and the league was not a major national sport.