Tommy Fury went from using his hands to using his pipes after beating Jake Paul on Sunday ... singing his heart out with his brother, Tyson, in the locker room to celebrate the huge win.
TNT was the happiest guy in the world after going 8 rounds with the Problem Child in Saudi Arabia ... and the man of the hour received a hero's welcome after exiting the ring.
"There's only one Tommy Fury," the crowd chanted as Tommy entered the room. "Walking along, singing a song, walking in a Fury wonderland."
Tyson couldn't have been more proud of his brother ... smiling from ear to ear as Tommy walked in with his new belt draped over his shoulder.
Tommy has all the bragging rights, but Jake has made it clear he's not riding off into the sunset ... and a rematch seems inevitable.
Jake took his first loss with respect ... thanking his fans for their support and praising the event.
"S*** happens, I guess," Jake said after the fight. "This is still the best job in the world."
"I'll be back -- no worries, cuz!!"