DREAM.6 took place on September 23, 2008, at Saitama Super Arena in Saitama, Japan, promoted by Fighting and Entertainment Group’s DREAM. The main event features Gegard Mousasi facing Ronaldo Souza in the Middleweight Grand Prix final to crown the first DREAM Middleweight Champion, with Mousasi advancing after a decision win over Melvin Manhoef and Souza submitting Zelg Galešić at DREAM.4. Other key bouts include Shinya Aoki vs. Todd Moore in a lightweight clash, Yoshihiro Akiyama vs. Masanori Tonooka, and Mirko Cro Cop vs. Alistair Overeem, which ends in a no-contest due to a knee strike. Additional fights showcase Hayato "Mach" Sakurai vs. Kuniyoshi Hironaka and Atsushi Yamamoto vs. Hideo Tokoro.