The folks at Bellator MMA have opted in on a champion vs. champion super fight between welterweight king Rory MacDonald and middleweight champion Gegard Mousasi. The promotion made the bout official Thursday afternoon. ESPN was first to report, stating, The promotion has booked a fight between middleweight champion Gegard Mousasi and welterweight champion Rory MacDonald on Sept. 29 in San Jose, Calif., multiple sources confirmed to ESPN. The fight will be contested at 185 pounds and Mousasi's middleweight title will be on the line. Should MacDonald win, he'd be the first fighter in Bellator history to hold two belts at the same time. The fight, which features two former UFC contenders, is arguably the biggest in Bellator's history.