2004 AFC Champions League

The 2004 AFC Champions League was the 23rd edition of the top-level Asian club football tournament and the 2nd edition under the current AFC Champions League title. The title was won by Al-Ittihad who defeated Seongnam Ilhwa Chunma in the final.

Al Ain were the defending champions, but were eliminated by Jeonbuk Hyundai Motors in the quarter-finals.

A total of 28 clubs were divided into seven groups of four, based on region i.e. East Asian and Southeast Asian clubs were drawn in groups E to G, while the rest were grouped in groups A to D. Each club played double round-robin (home and away) against fellow three group members, a total of six matches each. Clubs received three points for a win, one for a draw, and zero for a loss. The clubs were ranked according to points and tie breakers were in the following order:

The seven group winners along with the defending champion (Al Ain) advanced to the quarter-finals.

An open draw was held for the knockout stage; teams from the same group or the same association could not be drawn against each other. Each tie is played on a home-and-away two-legged basis. The away goals rule, extra time and penalty shoot-outs were used to decide the winner if necessary.

For this year the competition was restricted to clubs from countries considered 'mature' in the 'Vision Asia' paper of AFC President Mohamed Bin Hammam, with clubs from 'developing' countries entering the newly created AFC Cup and 'emerging' nations to enter the AFC President's Cup from 2005 onwards.

The first legs were played on 14 and 15 September, and the second legs were played on 21 and 22 September 2004.

Jeonbuk Hyundai Motors won 5–1 on aggregate.