The Australian Football League (AFL) is the pre-eminent professional competition of Australian rules football. It was originally named the Victorian Football League (VFL) and was founded in 1896 as a breakaway competition from the Victorian Football Association (VFA), with its inaugural season in 1897. It changed its name to Australian Football League in 1990 after expanding its competition to other Australian states in the 1980s. The AFL publishes its Laws of Australian football, which are used, with variations, by other Australian rules football organisations.

The AFL competition currently consists of 18 teams spread over Australia's five mainland states, with Tasmania to join the league as its 19th team in 2028. AFL premiership season matches have been played in all states and mainland territories, as well as in New Zealand and China to expand its audience.

The AFL premiership season currently consists of a 23-match regular (or home-and-away) season, which runs from March to September. The team with the best record at the end of the home-and-away season is awarded the minor premiership; the top eight teams then play off in a four-round finals series, culminating in the AFL Grand Final, which is normally held at the Melbourne Cricket Ground each year. The grand final winners are termed the premiers, the most important team prizes for which are the premiership cup and flag. Carlton, Collingwood and Essendon are the joint-most successful clubs in the competition, having each won 16 premierships. The Brisbane Lions are the reigning premiers, having won the 2025 AFL Grand Final.

Several of the AFL's current member clubs date back to the origins of Australian football and were instrumental in establishing the sport's popularity and the AFL. The oldest club is Melbourne Football Club, which wrote the first laws of the code, and Geelong, which date back to 1858 and 1859 respectively, while Melbourne University, also founded in 1859, is also one of the oldest clubs to have later participated in the competition.

The Victorian Football Association (VFA) was established in 1877 and quickly went on to become Victoria's football competition. During the 1890s, an off-field power struggle occurred between the VFA's stronger and weaker clubs, the former seeking greater administrative control commensurate with their relative financial contribution to the game. This came to a head in 1896 when it was proposed that gate profits, which were always lower in matches involving the weaker clubs, be shared equally among all teams in the VFA. After it was intimated that the proposal would be put to a vote, six of the strongest clubs—Collingwood, Essendon, Fitzroy, Geelong, Melbourne and South Melbourne—seceded from the VFA and later invited Carlton and St Kilda to join them in founding a new competition, the Victorian Football League (VFL). The remaining VFA clubs—Footscray, North Melbourne, Port Melbourne, Richmond and Williamstown—were given the opportunity to compete as junior sides at a level beneath the VFL but rejected the offer and remained for the 1897 VFA season.

The VFL's inaugural season occurred in 1897. It made several innovations early on to entice the public's interest, including an annual finals tournament, rather than awarding the premiership to the team with the best record through the season; and, the formal establishment of the modern scoring system, in which six points are awarded for a goal and one point for a behind.

Although the VFL and the VFA continued to compete for spectator interest for many years, the VFL quickly established itself as the premier competition in Victoria. In 1908, the league expanded to ten teams, with Richmond crossing from the VFA and University Football Club from the Metropolitan Junior Football Association. Professionalism began from the 1911 season, with clubs permitted to pay players beyond the reimbursement of expenses for the first time. University, after three promising seasons, finished last each year from 1911 until 1914, including losing 51 matches in a row, in part caused by its players' focus on their studies rather than football and in part because it had chosen to remain amateur; as a result, the club withdrew from the VFL at the end of 1914.

The premiers of the Victorian Football League and the premiers of the South Australian Football League met in a playoff matches for the Championship of Australia beginning in 1888 with a 3-game playoff between South Melbourne from the VFL and the Norwood the most successful club in the SAFA. Matches where then held sporadically during the 1890s as single game playoffs and then annually from 1907 until 1914 (except 1912). South Australian clubs won 8 of the 11 Titles of which Port Adelaide was the most successful winning four titles in 1890, 1910, 1913 and 1914. The majority of the matches were held in South Australia at Adelaide Oval. Following the outbreak of World War 1 the Championship playoff ceased and wasn't revived until 1968.