American football, known in the United States and Canada simply as football, is a competitive team sport. The object of the game is to score points by advancing the football into the opposing team's end zone. The ball can be advanced by carrying the ball, or by throwing or handing it from one teammate to the other. Points can be scored in a variety of ways, including carrying the ball over the goal line, throwing the ball to another player past the goal line or kicking it through the goal posts on the opposing side. The winner is the team with the most points when the time expires and the last play ends. However, tied games can occur. Outside of the United States and Canada, the sport is usually referred to as American football (or sometimes as gridiron or gridiron football) to differentiate it from other football games.

American football is the most popular spectator sport in the United States. In surveys of Americans, pluralities of respondents consider it to be their favorite sport. Football's American TV viewership ratings far surpass those of other sports. The NFL Football championship game, entitled the "Super Bowl", continually scores the highest ratings of any televised event on American television. [1] [2] The 32-team National Football League (NFL) is the only major professional American football league. Its championship game, the Super Bowl, is watched by nearly half of U.S. television households and is also televised in over 150 other countries. The day of the game, Super Bowl Sunday is a day when many fans host game watching parties and invite friends and family over to eat and watch the game.[3] It is considered by many to be the year's biggest day for "stay at home parties

College football is also popular throughout North America. Four college football stadiums (Michigan Stadium, Beaver Stadium, Neyland Stadium, Ohio Stadium), seat more than 100,000 fans and regularly sell out. Even high school football games can attract more than 10,000 people in some areas. The weekly autumn ritual of college and high-school football�which includes marching bands, cheerleaders and parties (including the ubiquitous tailgate party)�is an important part of the culture in much of smalltown America. It is a long-standing tradition in the United States (though not universally observed) that high school football games are played on Friday, college games on Saturday, and professional games on Sunday (with an additional professional game on Monday nights). Certain fall and winter holidays�most notably Thanksgiving and New Years' Day�have traditional football games associated with them. Football is played recreationally by amateur club and youth teams (e.g., the Pop Warner little-league programs). There are also many "semi-pro" teams in leagues where the players are paid to play but at a small enough salary that they generally must also hold a full-time job. The NFL operates a developmental league, NFL Europa, with teams in five German cities and one in the Netherlands. The professional Canadian Football League plays under Canadian rules. The sport is popular as an amateur activity in Mexico and American Samoa and to a lesser extent in Japan, Europe, Korea, New Zealand and Australia. Organized football is played almost exclusively by men and boys, although a few amateur and semi-professional women's leagues have begun play in recent years.

American football is played on a rectangular field 120 yards (110 meters) long by 53 1/3 yards (49 meters) wide. The longer boundary lines are sidelines, while the shorter boundary lines are end lines. Near each end of the field is a goal line; they are 100 yards apart. A scoring area called an end zone extends 10 yards beyond each goal line to each end line. Yard lines cross the field every 5 yards, and are numbered from each goal line to the 50-yard line, or midfield (similar to a typical rugby league field). Two rows of lines, known as inbounds lines or hash marks, parallel the side lines near the middle of the field. All plays start with the ball on or between the hash marks. At the back of each end zone are two goal posts (also called uprights) that are 18.5 feet (5.6 m) apart (24 feet (7.3 m) in high school). The posts are connected by a crossbar 10 feet (3 m) from the ground. Each team has 11 players on the field at a time. However, teams may substitute for any or all of their players, if time allows, during the break between plays. As a result, players have very specialized roles, and almost all of the 46 active players on an NFL team will play in any given game. Thus, teams are divided into three separate units: the offense, the defense and the special teams.

A standard football game consists of four 15-minute (typically 12 minutes in high school football) quarters, with a half-time intermission after the second quarter. The clock stops after certain plays; therefore, a game can last considerably longer (often more than three hours in real time). If an NFL game is tied after four quarters, the teams play an additional period lasting up to 15 minutes. In an NFL overtime game, the first team that scores wins, even if the other team does not get a possession�this is referred to as sudden death. In a regular-season NFL game, if neither team scores in overtime, the game is a tie. In an NFL playoff game, additional overtime periods are played, as needed, to determine a winner. College overtime rules are more complicated and are described in Overtime (sport).