Australian rules football and Gaelic football are codes of football, from Australia and Ireland respectively, which have similar styles and features of play. Notably both are dominated by kicking from the hand and hand passing as well as rules requiring the ball is bounced by a player running in possession, both have a differentiated scoring system, with higher and lower points values for different scoring shots, both have no offside rule, and both allow more physical contact and players on the field than other football codes - 15 in gaelic football, 18 in Australian Rules.

Although there are also many differences, the similarities have allowed a hybrid game to be played, with a regular International rules football series between top Australian AFL players and Irish GAA players.

It was a popular assumption from the 1930s to the late 1980s that Irish football is the basis for Australian football, based primarily on the premise that Ireland is older than Australia and the two games look similar.Centre for Tasmanian Historical Studies Bulletin, v.3, no.2, pp. 49–50 and; B. W. O'Dwyer, 1989, "The Shaping of Victorian Rules Football", Victorian Historical Journal, v.60, no.1.Richard Davis, 1991, "Irish and Australian Nationalism: the Sporting Connection: Football & Cricket" The correlation between Gaelic football and Australian rules football also led to a belief that caid played some part in the origins of Australian rules football. Some historians have cited questionable cause as a reason for the assumption, while others suggest reverse causation as a possible scenario. Nevertheless the relationship of Irish football to Australian football and a hypothetical role in the Origins of Australian rules football remains the subject of debate. While there are some mentions of Irish playing football in Australia (English and Scottish foot-ball were far more common) before the formation of the Melbourne Football Club, there is no specific mention of either "Caid", "Irish football" or "Gaelic football" in Australian newspapers of the time. The earliest mention from an Irish sources in Australia in 1889 was that the old mob football had very little in common with modern Gaelic football which upon first appearance in 1884 was received as more a hybrid of English and Scotch football. Patrick O'Farrell, and Chris McConville along with Marcus De Búrca, have used similar logic to postulate that hurling (which was documented in Australia) was the influence, however modern hurling was not codified until 1879. Some historians claim that the similarities are largely coincidental, that there is only circumstantial evidence for a relationship between the two codes, and any resemblances are the result of something akin to parallel or convergent evolution. Most contemporary historians emphasise the influence of English public school football games.

More recent evidence primarily from Irish and English researchers including Tony Collins, Joe Lennon, Geoffrey Blainey and Aaron Dunne point to the GAA creating Gaelic Football as a hybrid of existing football codes (codifier Maurice Davin in an effort to differentiate from rugby has been found to have been making extensive notes on Association Football (soccer) from which some of the rules were based),Wrestling with the early rules of Gaelic football Paul Rouse for The Irish Examiner 20 January 2017 and the Victorian Rules of 1866 and 1877 (which the modern Australian rules is based on), which were popular and widely distributed. More recently direct references to the published Victorian rules have been found in the rules of the founding Gaelic football club in Ireland, the Commercial Club of Limerick from the 1870s indicating that Australian football found its way to Ireland even earlier than this, perhaps in a similar fashion to the way it was introduced to the colonies of New South Wales, Queensland and New Zealand.

In 1967, following approaches from Australian rules authorities, there was a series of games between an Irish representative team and an Australian team, under various sets of hybrid, compromise rules. In 1984, the first official representative matches of International rules football were played, and the Ireland international rules football team now plays the Australian team annually each October. Since the 1980s, some Gaelic players, such as Jim Stynes and Tadhg Kennelly, have been recruited by the professional Australian Football League (AFL) clubs and have had lengthy careers with them.

Aside from game-play, a social difference between the codes is that Gaelic football is strictly amateur, whereas Australian football offers professional (Australian Football League), (AFL Women’s) and semi-professional (VFL, SANFL, WAFL, etc.) levels of competition, providing a strong financial lure for Irish players to switch to Australian football.

Origins

Gaelic football The earliest record of a recognised precursor to the modern game date from a match in County Meath in 1670, in which catching and kicking the ball was permitted. The earliest recorded inter-county match in Ireland was one between Louth and Meath, at Slane, in 1712, about which the poet James Dall McCuairt wrote a poem of 88 verses beginning "Ba haigeanta".

Gaelic football was codified by the Gaelic Athletic Association (GAA) in 1887. GAA founder and Irish nationalist Michael Cusack wanted the rules of Gaelic football to differ from rugby union, which was making headway in Ireland at the time.

Australian rules football Australian rules football was codified in 1859 by members of the Melbourne Football Club. The first rules were devised by the Australian-born Tom Wills, who was educated at Rugby School; Englishmen William Hammersley and J. B. Thompson, fellow students at Cambridge's Trinity College; and Irish Australian Thomas H. Smith, who played rugby football at Dublin University. Their knowledge of English public school football games, and the conditions and terrain of Melbourne's parklands, influenced the first rules of Australian football. It has been suggested that Wills was influenced by an Australian Aboriginal game, Marn Grook, as Wills grew up in an area where the game was played by local tribes.Touchstone of Australian Life by Martin Flanagan Historians such as Geoffrey Blainey have argued that the origins of Australian rules football lie purely with rugby and other English public school games.

Traditional Irish football in Australia In 1843, Irish immigrants in South Australia celebrated St Patrick's day by playing a game of caid in Thebarton.1843 'THE AGRICULTURAL AND HORTICULTURAL SHOW.', South Australian Register (Adelaide, SA : 1839 - 1900), 18 March, p. 4., viewed 07 Nov 2017, http://nla.gov.au/nla.news-article27444196

Some historians have argued that Gaelic football influenced Australian football. For example, Patrick O'Farrell has pointed out that the Irish sport of hurling, which has similar rules to Gaelic football, was played in Australia as early as the 1840s, and may also have been an influence on the Australian game.Cited in Davis, p.49n B. W. O'Dwyer points out that Australian football has always been differentiated from rugby football by having no limitation on ball or player movement (in the absence of an offside rule), the need to bounce the ball (or toe-kick it, known as a solo in Gaelic football) while running, punching the ball (hand-passing) rather than throwing it, and other traditions. As O'Dwyer says:B. W. O'Dwyer, March 1989, "The Shaping of Victorian Rules Football", Victorian Historical Journal, v.60, no.1.

O'Dwyer's argument relies heavily on the presence of Irish immigrants on the Victorian goldfields during the Victorian gold rushes of the 1850s, and a comparison of the two modern games. There is no archival evidence to prove a direct influence of caid on Australian football.

Irish sources in Australia in 1889 state that the old mob football played in Ireland bore very little resemblance to modern Gaelic football which upon first appearance in 1884 was received by the Irish as more a hybrid of English and Scotch football.

Australian rules football in Ireland British historian Tony Collins argues strongly that the GAA hybridised Australian rules and soccer to differentiate from rugby, however takes the view that the development of Australian rules in the late 19th century was likely influenced by traditional Irish hurling (rather than Irish football) and points out that this sharing of codes across sports is a natural byproduct of globalisation.Collins, Tony. How Football Began: A Global History of How the World's Football Codes Were Born. New York: Routledge, 2019.

Bill Mandle notes that although it lacks evidence that Gaelic Football's come into being in 1880s is a possible indication of Irish Australian influence back home.

Arguments were as follows:

The two codes were virtually identical in 1885 Aaron Dunne, an Irish sports writer and historian, raises the similarity between the 1885 GAA rules and the 1866 Victorian ones arguing that it is obvious that the GAA used the Victorian rules as a template for Gaelic Football. The similarities included the length and width of the field, the number of players per team (20 vs 21) the distance between the posts, goals and behinds used in the scoring system, the requirement not to throw the ball and the requirement to bounce the ball, everything apart from the shape of the field.

Adding weight to this theory is former Gaelic footballer Joe Lennon's thorough post-doctoral research analysing of accounts of caid and GAA codified rules against the Melbourne Football Club rules of 1959 and Victorian Rules of 1866 and 1877 appear to indicate direct copying, some virtually verbatim by the GAA from Australian rules and other football codes, but primarily from the 1866 and 1877 Victorian rules.Towards a Philosophy for Legislation in Gaelic Games Lennon, Joe. Dublin City University 1993. Pg 633, 638, 649, 658, 759 For example early codified Gaelic called for Australian rules style behind posts (not present in caid and later removed) with 5 point goals scoring (later changed to 3) and 1 point "behind"s all borrowed from Australian Rules, and Rule 27 in reference to kicking styles, Rule 15 relating to foul play and rules dictating playing equipment appear to be directly borrowed from the Victorian Rules. Early Victorian Rules was played with also a round ball until the introduction of the Sherrin in the 1880s. Other than the directly copied rules, analysts argue that so many of the rules are so similar to the Victorian Rules that it would have been impossible for the GAA rule makers not to have obtained a deep knowledge of the Laws of Australian Football.

Australian founders had little to no knowledge of Gaelic football Jack Worral in 1926 wrote that the "Father of Australian Football" H. C. A. Harrison who had sought to "code of our own" in 1859 was genuinely surprised in 1927 to learn that the Irish had been playing a very similar game since the 1880s.

Gaelic football did not exist until the 1880s Geoffrey Blainey in 2010 wrote:Blainey, Geoffrey. A Game of Our Own: The Origins of Australian Football. Black Inc., 2010. , p. 196.

Irish historian Garnham, citing R.M. Peter's Irish Football Annual of 1880, argued that Gaelic Football did not actually exist before the 1880s and curious on the origin of the distinctive features was of the belief that clubs from England in 1868 were most likely introduced elements of their codes including the "mark" (a decade after it had been introduced in Australia) and scoring by kicking between the upright posts. He believed these attributes to have been introduced by English clubs Trinity (1854) and Blackheath (1862) who had their own distinctive rules, rather than from those of Melbourne. However these English games were otherwise dissimilar to both Gaelic Football or Australian Football of 1885.

There was a motive and means for borrowing the rules