2009 J.League Division 1
The 2009 J.League Division 1 season was the 45th season of the top-flight club football in Japan and the 17th season since the establishment of J.League Division 1. The season started on March 7 and ended on December, 5.
A total of eighteen clubs participated in double round-robin format. At the end of the season, top three clubs received automatic qualification to the following years' AFC Champions League. Also starting this season, the bottom three clubs were relegated to J.League Division 2 by default.
Kashima Antlers became the first Japanese club win J.League Division 1 in three straight seasons.
Clubs
The following eighteen clubs participated in J.League Division 1 during the 2009 season. Of these clubs, Sanfrecce Hiroshima and Montedio Yamagata were newly promoted clubs.| Club name | Home town | Note |
| Albirex Niigata | Niigata & Seirō, Niigata | |
| FC Tokyo | Tokyo | |
| Gamba Osaka | Suita, Osaka | 2009 ACL participant |
| JEF United Chiba | Chiba & Ichihara, Chiba | |
| Júbilo Iwata | Iwata, Shizuoka | |
| Kashima Antlers | Southwestern cities/towns of Ibaraki | 2009 ACL participant Two-time defending champions |
| Kashiwa Reysol | Kashiwa, Chiba | |
| Kawasaki Frontale | Kawasaki, Kanagawa | 2009 ACL participant |
| Kyoto Sanga | Southwestern cities/town in Kyoto | |
| Montedio Yamagata | All cities/towns in Yamagata | Promoted from J2 League in 2008 |
| Nagoya Grampus | Nagoya, Aichi | 2009 ACL participant |
| Oita Trinita | All cities/towns in Ōita | |
| Omiya Ardija | Saitama | |
| Sanfrecce Hiroshima | Hiroshima | Promoted from J2 League in 2008 |
| Shimizu S-Pulse | Shizuoka | |
| Urawa Red Diamonds | Saitama | |
| Vissel Kobe | Kobe, Hyōgo | |
| Yokohama F. Marinos | Yokohama & Yokosuka |
League format
Eighteen clubs will play in double round-robin format, a total of 34 games each. A club receives 3 points for a win, 1 point for a tie, and 0 points for a loss. The clubs are ranked by points, and tie breakers are, in the following order:- Goal differential
- Goals scored
- Head-to-head results
- Disciplinary points
;Changes from previous year
- Bottom three clubs are relegated by default; during 2004–2008 season, the 16th-place club needed to win playoffs to avoid relegation.
- The fourth foreign player slot is introduced.