The AFC Cup is an annual international association football competition between domestic clubs run by the Asian Football Confederation (AFC). Qualification to the competition is available to clubs from AFC-affiliated countries that fall into the AFC's 'developing nations' category as laid out in their 'Vision Asia' document. Countries which are 'emerging' nations are eligible to participate in the AFC Cup qualifying play-off, where as countries which are 'mature' nations are entered into the AFC Champions League.
The 'developing nations' are the fourteen 'next-best' countries that lie outside the top-14 countries in the AFC region which send their clubs to the more prestigious AFC Champions League. Before the reform in competition format that took place in 2009, the two competitions were not interlinked as the UEFA Champions League and the UEFA Europa League are in Europe, and AFC Champions League losers did not compete in the Cup. Following the reform in 2009, finalists of the AFC Cup meeting AFC's criteria and certain other eligible teams are allowed to compete in the qualifying round of AFC Champions League with the losers demoted to play in the AFC Cup.
Kuwait SC are the most successful club in the competition's history, having won three titles. Clubs Kuwait have won four titles, making them the most successful nation in the competition. Ever since the inauguration of the competition in 2004, the finalists of each edition have been dominated by clubs from West Asia.
Teams from only 27 AFC countries have reached the group stage of the AFC Cup. The allocation of those teams by member country is listed below. Number sign (#) represent at least one team that failed at AFC Champions League qualification; Asterisks (*) represent at least one team was eliminated in qualification; 28 AFC countries have had teams participate in qualification, though a country (Nepal) that has never reached the group stage are not shown.