A mark in Australian rules football is the catch of a kicked ball which earns the catching player a free kick. The catch must be cleanly taken, or deemed by the umpire to have involved control of the ball for sufficient time. A tipped ball, or one that has touched the ground cannot be marked. Since 2002, in most Australian competitions, the minimum distance for a mark is 15 metres (16 yards or 49 feet).
Marking is one of the most prevalent skills in Australian football, and aiming for a teammate who can mark their kick is the primary focus of any kicking player not kicking for goal. Marking can also be one of the most spectacular and distinctive aspects of the game, and the best mark of the AFL season is awarded with the Mark of the Year, with similar competitions running across smaller leagues.
The top markers in the Australian Football League, like Jason Dunstall and Jonathan Brown took an average of over eight marks per game. An AFL match between St Kilda and Port Adelaide in 2006 set a record of 303 marks in a single game.
Upon taking a mark, the umpire will blow the whistle to signify the mark and a player is entitled to an unimpeded kick of the ball. The nearest opposition player stands on the spot where the player marked the ball, which is also known as 'the mark' and he becomes 'the man on the mark.' When awarded the free kick, the player can choose to forego their kick to play-on and run into space, with the defending players then allowed to tackle as normal. If the player takes to long to complete their free kick, the umpire will call play-on, rescinding the award of the free kick, which also allows the defenders to tackle as normal.
A mark must be caught cleanly, with the player having complete control of the ball, even if only for a short time. As such, if the ball is punched out from between the player's hands after it is caught, or the ball is dislodged upon hitting the ground, a mark is still paid, even if the ball was held for only an instant.
Although the rules make no provision for two players marking the ball simultaneously, by convention the umpire will award the mark to the man in front, i.e. the player who has the front position in the marking contest. If he cannot determine which player is in front, then a ball-up will result.
The mark has been included in the compromise rules used in the International Rules Football series between teams from Australia and Ireland since 1984.
The current minimum distance for a mark is 15 metres. However prior to the 1880s there was no minimum distance and "little marks" or short passes were extremely common and some noted that it resulted in less congestion around the ball. The distance has been changed over time by the AFL along with the introduction of a "protected zone" around the kicker which no player may enter. A 4.5 metre minimum was introduced in the 1880s. This was later reduced to 1.8 metres in 1887. For many decades the distance was 10 metres. It was increased to its current distance in 2002.
The minimum distance cannot be accurately measured and confusion can result from a play-on call when a kick is judged "not 15". Rule reformers would have this distance increased or abandon the requirement altogether.
Currently only one player may stand the mark and there is a protected zone around the kicker which other players may not enter. However prior to the 1924 it was not required for an umpire to nominate a single player to stand the mark. Prior to 2021 players were free to move anywhere behind the mark line. The AFL introduced the "Stand Rule" which states that the player standing the mark may not move at all, or a distance penalty will apply. The rule was introduced to reduce defensive play, encourage direct attacking play and increase scoring, however it has attracted substantial criticism from fans. It resulted in lower field kicks, less contested marks, reduced running, reduced contact, reduced direct attacking and less scoring as teams increasingly turn to defend the forward 50 and intercept marks.
The combination of kick and mark as the primary means for advancing the ball has been a distinctive feature of Australian football ever since the first rules were created in 1859. Other forms of football descended from English public school football games of the 19th century have featured a fair catch, with similar rules to the mark. It was abolished early in the development of soccer and is only used occasionally in rugby union and American football.
The origin of the term has a few possible sources. In rugby and the early days of soccer, a player would shout 'mark' and mark the ground with their foot. It was formerly a requirement in the Australian game to make such a mark but this is no longer the case. Sometimes a cap which formed part of the uniform was used to show where the fair catch was taken.
Another source of the term may have been from the traditional Aboriginal game of Marn Grook, which is said to have influenced founder Tom Wills' development of the early forms of Australian football. It is claimed that in Marn Grook, jumping to catch the ball, called "mumarki", an Aboriginal word meaning "to catch", results in a free kick. 
In Australian football, marks are often described in combination of the following ways.
While the Mark of the Year competition has produced many famous marks, other marks include:
In the 1970 Grand Final before a record crowd of 121,696, Carlton full forward, and giant of the game, Alex Jesaulenko, took one of the most inspirational marks in the history of 'the Australian game.' Leaping high for a specky over Collingwood's Graeme Jenkin just before half time, the mark inspired a Carlton side that was behind by 44 points at the half. It was retroactively classified as the Mark of the Year.
Sydney's Leo Barry leapt into history with his match-saving mark in the final seconds of the 2005 grand final against the West Coast Eagles to seal the game. His contested overhead mark was taken in a congested pack of three teammates and three opposition players.
Shaun Smith's and Gary Ablett's shared title of Mark of the Century.
St Kilda/South Melbourne player Roy Cazaly was renowned for his high marks, giving rise to the catchphrase and song "Up There Cazaly".
Spoiling is the technique typically employed by opposition defenders to legally stop a player from catching the ball. It is performed as a punching action by hand or fist just before the opposing player has caught the ball in their hands.
The rules are quite strict on defensive spoiling methods. Players are not allowed to push other players out of marking contests or make forceful front on contact with an opponent in a marking contest, if they are not simultaneously attempting to mark or spoil the ball. Also, no high contact is allowed unless such contact is incidental to attempting to mark or spoil the ball.
Deliberately taking, hacking or chopping the arms is an infringement committed by players which will result in a free kick.
The arm interference free kick was introduced as a specific free kick in the AFL and its affiliates in 2005, although it was paid as a blocking, striking or holding free kick previously. The free kick was designed predominately to make it easier for forwards to take contested marks by not allowing defending player to punch or pull a marking player's outstretched arms in a marking contest.
The rule was introduced by the AFL amidst on-going calls from fans and commentators to take action against the defensive tactic of flooding. The rule does directly limit the effectiveness of defenders, but the AFL has never stated whether or not flooding was the reason for the change.