It looked as if KSI had done enough to claim the win over Fury, but the judges thought otherwise.
Fury suffered a points deduction in the second round for repeatedly hitting the back of his opponent's head, which left fans believing he needed a knockout to win.
One judge scored it a draw at 57-57 and the other judges both went with 57-56.
Speaking after the fight, KSI called the decision a "robbery" - but didn't talk to the press.
Plenty of names in the boxing world came to the YouTuber's defence, including Chris Eubank Jr, Eddie Hearn and DAZN CEO Joe Markowski.
Despite the loss, any post-fight questions surrounding a rematch were left unanswered by KSI and completely refused by Fury - who said he wants to move away from the influencer boxing scene.
