KSI, 29, dropped Fournier, 40, in the second round, leaving the businessman and former professional boxer unable to beat the referee’s count.
However, replays showed that KSI (real name Olajide Olatunji) had actually hit Fournier with an accidental elbow.
Fournier said on his Instagram story that he will be appealing the result.
“I knew fighting the promoter there would be every angle in his [favour] but to call this a KO instead of a disqualification after an intentional elbow is disgusting!” Fournier posted. “We will be appealing this decision Monday and I hope both [KSI and Misfits Boxing, and Professional Boxing Association] do the right thing and show their integrity to the sport of boxing!”
“He cheated – clear, black and white,” Fournier also told Fred Peck. “You’ve all seen the replays, it’s gone viral, it’s all over the world.
“He hit me with a clean elbow, and the ref was right there, watched it. Obviously [KSI] owns the promotion; when you’re fighting the promoter on his own show... I’ve never been cheated like that in my life.
“I can’t believe... I came on this promotion to teach kids that you’ve got to do the right things, got to be ethical, got to work hard for everything you get – not to cheat and you win.
“I saw the punch go past my face, and then he hits me with an elbow. Literally, I felt bone.
“Of course you’ve got to run it back; he should be disqualified, that should go down as a loss.”
Fournier holds a professional boxing record of 9-0 with nine knockout wins, and he previously lost to David Haye on points in an exhibition fight in 2021.
Meanwhile, KSI’s win on Saturday was his fourth straight knockout victory in as many exhibition fights.
Click here to subscribe to The Independent’s Sport YouTube channel for all the latest sports videos.