Australian football, also commonly referred to as football, or Aussie rules, colloquially as footy, and historically as Australasian football or Victorian football, is a variant of football played between two teams of 18 players, plus four interchange players, outdoors on large oval-shaped grass fields (often modified cricket fields), with a ball in the shape of a prolate spheroid.

The primary aim of the game is to score goals by kicking the ball between the middle two posts of the opposing goal. The winner is the team with the higher total score at the end of the fourth quarter. Except for special circumstances, if the score is tied a draw is declared.

Players may use any part of their body to advance the ball. The primary methods are kicking, handballing and running with the ball. There are rules on how the ball can be handled, for example players running with the ball must intermittently bounce or touch it on the ground, throwing the ball is not allowed and players must not get caught holding the ball. Unlike most similar sports, there is no offside rule, and players can roam the field freely. Possession of the ball is in dispute at all times except when a free kick is paid. A distinctive feature of the game is the mark, where players anywhere on the field who catch a ball from a kick (with specific conditions), are awarded a free kick. Australian rules is a contact sport, in which players can tackle using their hands or use their whole body to obstruct opponents. Dangerous physical contact (such as a pushing an opponent in the back), interference when marking and deliberately slowing the play are discouraged with free kicks, distance penalties or suspension, depending on the seriousness of the infringement. Frequent physical contests, aerial marking or "speckies", fast movement of both players and the ball and high scoring are the game's main attributes.

Details of the game's origins in Australia are obscure and still the subject of much debate. Australian football became organised in Melbourne in 1858 with a series of experimental rules in a bid to keep cricketers fit during the winter months and in 1859 the first laws of the game were published by the Melbourne Football Club.

Australian football is a major participation and spectator sport in Australia and in Nauru. The most prestigious and only national competition in Australia is the Australian Football League (AFL), which culminates in the annual AFL Grand Final, currently the fourth highest attended club championship event in the world. The AFL has governed the sport nationally since 1993 and internationally since 2005 through the AFL Commission and the AFL Laws of the Game Committee. The game is also played at amateur level in several countries and in several variations.