The 2021 AFC Champions League knockout stage was played from 13 September to 23 November 2021. A total of 16 teams competed in the knockout stage to decide the champions of the 2021 AFC Champions League.
The group winners and three best runners-up in the group stage from each region advanced to the round of 16, with both West Region (Groups AâÂÂE) and East Region (Groups FâÂÂJ) having eight qualified teams. <section begin=Qualified teams /> <section end=Qualified teams /> <section begin=Combination table /><noinclude>
If two group winners played each other, the group winner marked with * hosted the match. </noinclude>
<noinclude>
One-leg matches (13âÂÂ14 September 2021)
</noinclude>
One-leg matches (14âÂÂ15 September 2021)
<section end=Combination table />
<section begin=Format /> In the knockout stage, the 16 teams played a single-elimination tournament, with the teams split into the two regions until the final. All ties were played as a single-leg match (Regulations Article 9.1). Extra time and penalty shoot-out were used to decide the winners if necessary (Regulations Article 9.3 and 10.1).<section end=Format />
The schedule of each round was as follows.
The bracket of the knockout stage was determined as follows:
<section begin=Bracket /> <section end=Bracket />
<section begin=Round of 16 /> The round of 16 was played over one leg, with the matchups determined by the combination tables based on which group runners-up qualified.
|+West Region
|+East Region
<section end=Round of 16 />
<section begin=Quarter-finals /> The quarter-finals were played over one leg, with the matchups and home team decided by draw held on 17 September at 15:00 (UTC+8) in Kuala Lumpur, Malaysia.
|+West Region
|+East Region
<section end=Quarter-finals />
<section begin=Semi-finals /> The semi-finals were played over one leg.
|+West Region
|+East Region
<section end=Semi-finals />
<section begin=Final />
The final was played over a single leg on 23 November. The host was determined on a rotational basis, with the match hosted by team from the West Region in odd-numbered years (Regulations 9.1.2). <section end=Final />