2018 AFC Champions League
The 2018 AFC Champions League was the 37th edition of Asia's premier club football tournament organized by the Asian Football Confederation, and the 16th under the current AFC Champions League title.
Kashima Antlers won the title for the first time, defeating Persepolis in the final, and qualified as the AFC representative at the 2018 FIFA Club World Cup in the United Arab Emirates.
Urawa Red Diamonds were the title holders, but they were unable to defend their title as they finished seventh in the 2017 J1 League and were eliminated in the fourth round of the 2017 Emperor's Cup, thus did not qualify for the tournament. It marked the second season in a row without title holders after Jeonbuk Hyundai Motors were disqualified in 2017 as a result of their involvement in a match-fixing scandal in 2016.
Association team allocation
The AFC Competitions Committee proposed a revamp of the AFC club competitions on 25 January 2014, which was ratified by the AFC Executive Committee on 16 April 2014. The 46 AFC member associations are ranked based on their national team's and clubs' performance over the last four years in AFC competitions, with the allocation of slots for the 2017 and 2018 editions of the AFC club competitions determined by the 2016 AFC rankings :- The associations were split into two regions:
- *West Region consists of the associations from the West Asian Football Federation, the Central Asian Football Association, and the South Asian Football Federation.
- *East Region consists of the associations from the ASEAN Football Federation and the East Asian Football Federation.
- In each region, there are four groups in the group stage, including a total of 12 direct slots, with the 4 remaining slots filled through play-offs.
- The top 12 associations in each region as per the AFC rankings are eligible to enter the AFC Champions League, as long as they fulfill the AFC Champions League criteria.
- The top six associations in each region get at least one direct slot in the group stage, while the remaining associations get only play-off slots :
- *The associations ranked 1st and 2nd each get three direct slots and one play-off slot.
- *The associations ranked 3rd and 4th each get two direct slots and two play-off slots.
- *The associations ranked 5th each get one direct slot and two play-off slots.
- *The associations ranked 6th each get one direct slot and one play-off slot.
- *The associations ranked 7th to 12th each get one play-off slot.
- The maximum number of slots for each association is one-third of the total number of eligible teams in the top division.
- If any association gives up its direct slots, they are redistributed to the highest eligible association, with each association limited to a maximum of three direct slots.
- If any association gives up its play-off slots, they are annulled and not redistributed to any other association.
;Notes
Teams
The following 46 teams from 20 associations entered the competition.In the following table, the number of appearances and last appearance count only those since the 2002–03 season, when the competition was rebranded as the AFC Champions League.
| Team | Qualifying method | App |
 Al-Jazira | 2016–17 UAE Pro-League champions | 10th |
| Al-Wahda | 2016–17 UAE President's Cup winners | 9th |
| Al-Wasl | 2016–17 UAE Pro-League runners-up | 2nd |
 Al-Hilal | 2016–17 Saudi Professional League champions 2017 King Cup winners | 14th |
| Al-Ahli | 2016–17 Saudi Professional League runners-up | 10th |
 Persepolis | 2016–17 Persian Gulf Pro League champions | 7th |
| Esteghlal | 2016–17 Persian Gulf Pro League runners-up | 9th |
| Tractor | 2016–17 Persian Gulf Pro League 3rd place | 5th |
 Al-Duhail | 2016–17 Qatar Stars League champions | 7th |
| Al-Sadd | 2017 Emir of Qatar Cup winners 2016–17 Qatar Stars League runners-up | 13th |
| Al-Rayyan | 2016–17 Qatar Stars League 3rd place | 8th |
 Lokomotiv Tashkent | 2017 Uzbek League champions 2017 Uzbekistan Cup winners | 6th |
| Team | Qualifying method | App |
 Jeonbuk Hyundai Motors | 2017 K League Classic champions | 11th |
| Ulsan Hyundai | 2017 Korean FA Cup winners | 6th |
| Jeju United | 2017 K League Classic runners-up | 3rd |
 Kawasaki Frontale | 2017 J1 League champions | 6th |
| Cerezo Osaka | 2017 Emperor's Cup winners 2017 J1 League 3rd place | 3rd |
| Kashima Antlers | 2017 J1 League runners-up | 8th |
 Guangzhou Evergrande | 2017 Chinese Super League champions | 7th |
| Shanghai Shenhua | 2017 Chinese FA Cup winners | 8th |
 Sydney FC | 2016–17 A-League premiers 2017 A-League Grand Final winners | 4th |
| Melbourne Victory | 2016–17 A-League regular season runners-up | 6th |
 Buriram United | 2017 Thai League T1 champions | 7th |
 Kitchee | 2016–17 Hong Kong Premier League champions | 4th |
| Team | Qualifying method | App |
| Brisbane Roar | 2016–17 A-League regular season 3rd place | 5th |
| Chiangrai United | 2017 Thai FA Cup winners | 1st |
| Muangthong United | 2017 Thai League T1 runners-up | 7th |
| Eastern | 2016–17 Hong Kong Season Play-off winners | 2nd |
 FLC Thanh Hóa | 2017 V.League 1 runners-up | 1st |
 Johor Darul Ta'zim | 2017 Malaysia Super League champions | 4th |
;Notes
Schedule
The schedule of the competition was as follows.Qualifying play-offs
Preliminary round 1
Preliminary round 2
Play-off round
Group stage
| Tiebreakers |