AFC Champions League

The AFC Champions League (abbreviated as ACL) is an annual continental club football competition organised by the Asian Football Confederation. The competition is a continuation of the Asian Club Championship which had started in 1967.
A total of 40 clubs compete in the round robin group stage of the competition. Clubs from Asia's strongest national leagues receive automatic berths, with clubs from lower-ranked nations eligible to qualify via the qualifying playoffs, and they are also eligible to participate in the AFC Cup. The winner of the AFC Champions League qualifies for the FIFA Club World Cup.
The most successful clubs in the competition are Al-Hilal and Pohang Steelers with a total of three titles each. The reigning champions of the competition are Ulsan Hyundai, who won the competition for the second time in 2020.
History.
1967–1972: Asian Champion Club Tournament.
The competition started as the Asian Champion Club Tournament, a tournament for the champions of AFC nations, and had a variety of different formats, with the inaugural tournament staged as a straightforward knockout format and the following three editions consisting of a group stage. 
While Israeli clubs dominated the first four editions of the competition, this was partly due to the refusal of Arab teams to face them. In 1970, Lebanese side Homenetmen refused to play against Hapoel Tel Aviv in the semi-final, giving Hapoel a forfeit into the final, while in 1971, Al-Shorta of Iraq refused to play against Maccabi Tel Aviv on three occasions: in the preliminary round, the group stage, and the final itself. The Iraqi media considered Al-Shorta as the tournament's winners, and the team held an open top bus parade in Baghdad. After the 1972 edition had to be cancelled by the AFC when two Arab teams refused to commit to playing against Israeli side Maccabi Netanya, the AFC discontinued the competition, and Israel were expelled from the confederation.
1985–2002: Return as the Asian Club Championship.
Asia's premier club tournament made its return in 1985 as the Asian Club Championship, and in 1990, the Asian Football Confederation introduced the Asian Cup Winners' Cup, a tournament for the cup winners of each AFC nation. The 1995 season saw the introduction of the Asian Super Cup, where the winners of the Asian Club Championship and Asian Cup Winners' Cup played against each other.
2002–present: AFC Champions League.
The 2002–03 season saw the Asian Club Championship, Asian Cup Winners' Cup and Asian Super Cup combine to become the AFC Champions League. League champions and cup winners would qualify for the qualifying playoffs with the best eight clubs from East Asia and the eight best clubs from West Asia progressing to the group stage. The first winners under the AFC Champions League name were Al-Ain, defeating BEC Tero Sasana 2–1 on aggregate. In 2004, 29 clubs from fourteen countries participated and the tournament schedule was changed to March–November. In the group stage, the 28 clubs were divided into seven groups of four on a regional basis, separating East Asian and West Asian clubs to reduce travel costs, and the groups were played on a home and away basis. The seven group winners along with the defending champions qualified to the quarterfinals. The quarter-finals, semi-finals, and finals were played as a two-legged format, with away goals, extra time, and penalties used as tie-breakers.
The 2005 season saw Syrian clubs join the competition, thus increasing the number of participating countries to 15, and two years later, following their transfer into the AFC in 2006, Australian clubs were also included in the tournament. Owing to the lack of professionalism in Asian football, many problems still existed in the tournament, such as on field violence and late submission of player registration. Many blamed the lack of prize money and expensive travel cost as some of the reasons. The Champions League expanded to 32 clubs in 2009 with direct entry to the top ten Asian leagues. Each country received up to 4 slots, though no more than one-third of the number of teams in that country's top division, rounded downwards, depending on the strength of their league, league structure (professionalism), marketability, financial status, and other criteria set by the AFC Pro-League Committee. The assessment criteria and ranking for participating associations would be revised by AFC every two years.
The current format sees the eight group winners and eight runners-up qualify to the Round of 16, in which group winners play host to the runners-up in two-legged series, matched regionally, with away goals, extra time, and penalties used as tie-breakers. The regional restriction continues all the way until the final, although clubs from the same country cannot face each other in the quarterfinals unless that country has three or more representatives in the quarterfinals. Since 2013, the final has also been held as a two-legged series, on a home and away basis.
Beginning from 2021, the group stage will be expanded from 32 to 40 teams, with both the West and East Regions having five groups of four teams. The slot allocation for the top six member associations in each region will remain unchanged.
Format.
Qualification.
As of the 2009 edition of the tournament, the AFC Champions League has commenced with a double round-robin group stage of 32 teams, which is preceded by qualifying matches for teams that do not receive direct entry to the competition proper. Teams are also split into east and west zones to progress separately in the tournament.
The number of teams that each association enters into the AFC Champions League is determined annually through criteria as set by the AFC Competitions Committee. The criteria, which is a modified version of the UEFA coefficient, measures such thing as marketability and stadia to determine the specific number of berths that an association receives. The higher an association's ranking as determined by the criteria, the more teams represent the association in the Champions League, and the fewer qualification rounds the association's teams must compete in.
Tournament.
The tournament proper begins with a group stage of 40 teams, divided into ten groups. Seeding is used whilst making the draw for this stage, with teams from the same country not being drawn into groups together. The group stage is divided into two zones; the first zone is the five East Asian groups and the other zone is the five West Asian groups. Each team meets the others in its group home and away in a round-robin format. The winning team and the runners-up from each group then progress to the next round.
For this stage, the winning team from one group plays against the runners-up from another group from their zone of the group stage. The tournament uses the away goals rule: if the aggregate score of the two games is tied after 180 minutes, then the team who scored more goals at their opponent's stadium advances. If still tied the clubs play extra time, where the away goals rule is no longer applied. If still tied after extra time, the tie shall be decided by a penalty shootout. East and West zones continue to be kept part until the final.
The group stage and Round of 16 matches are played through the first half of the year (February–May), whilst the knock-out stage thereafter is played during the second half of the year (August–November). The knock-out ties are played in a two-legged format, including the final.
Allocation.
Teams from only 19 AFC countries have reached the group stage of the AFC Champions League. The allocation of teams by member countries is listed below; asterisks represent occasions where at least one team was eliminated in qualification prior to the group stage. 32 AFC countries have had teams participate in qualification, and countries that have never had teams reach the group stage are not shown.
Prize money.
The prize money for the 2020 AFC Champions League:
Marketing.
Sponsorship.
Like the FIFA World Cup, the AFC Champions League is sponsored by a group of multinational corporations, in contrast to the single main sponsor typically found in national top-flight leagues.
The tournament's current main sponsors are:
Video game.
The current license holder for the AFC Champions League video game is Konami with the Pro Evolution Soccer series. The license also includes the competing teams.
Records and statistics.
Performances by region.
Note: Israeli clubs, winners of the 1967, 1969 and 1971 editions, are not included.