Jake Paul challenged Saul 'Canelo' Alvarez moments after insisting his brother Logan defeated Floyd Mayweather.
Jake was ringside on Sunday in Miami to watch Logan valiantly go the eight-round distance with boxing legend Mayweather in an exhibition match.
Mayweather's inability to knock Logan out drew a sarcastic social media response from Canelo, who has inherited his status as the world's best boxer.
Jake responded to Canelo: "You can't sell pay-per-views. I would eat you alive."
He had earlier claimed that his brother was winning 4-2 against Mayweather heading into the seventh round (there were no judges or an official winner as per exhibition rules).
Jake posted afterwards: "My brother just beat Floyd Mayweather!"
He also teased "50-1" - a reference to Mayweather's trademark undefeated record being ended.
Jake, like his brother, stepped into the boxing ring to fight fellow YouTubers.
Whereas Logan lost to KSI, Jake has won all three of his professional matches.
He has knocked out social media influencer AnEsonGib, basketball player Nate Robinson and MMA fighter Ben Askren.
He next fights on August 28 against Tyron Woodley, a former UFC champion.