Jon Jones said victory felt "so sweet" after he controversially landed a unanimous points verdict over Dominick Reyes at UFC 247 in Houston.
The judges scored the fight 48-47, 48-47, 49-46 in favour of Jones, but Reyes was furious and said he had been "all over" the champion over the first three rounds.
UFC president Dana White revealed his children thought Reyes had done enough to get the decision and were plaguing him for answers over why Jones retained his light-heavyweight title.
With his success, Jones becomes the UFC fighter with the most wins in title fights, his tally of 14 one better than Georges St-Pierre's record.
And the 32-year-old American is now undefeated in his last 18 UFC fights, having last lost to Matt Hamill in 2009, when he was disqualified.
However, the crowd inside the Toyota Center saw a tight contest and Jones admitted he had been through a war in the octagon.
"He landed some hard hits. The fans like it when they see me get hit - it doesn't happen very often," Jones said.
"But at the same time, I landed some takedowns. I got his back on more than one occasion. ... A hard-earned victory but a victory."
He added, according to ESPN: "That's the way to make American history right there: hard-fought.
"It wasn't the most impressive victory, but nothing, absolutely nothing that has never been done before is easy. It is never easy. I left it all out there, showed the heart of a champion in the fifth round, and it's so sweet."
Jones, who certainly came on strong in the fourth and fifth rounds, was not in the mood for modesty after confirmation his reign as champion would continue.
"Obviously, my body is hurting, but this victory is so sweet. This fight helps to put me as one of the greatest American athletes of all time," he said.
Reyes, a 30-year-old from California who suffered his first loss, took a swipe at the 49-46 verdict against him, insisting that was a false reflection of the match-up.
He said: "I do feel disrespected. I know I won that fight ... I made Jon Jones look like just a man. I brought the fight to him.
"I had him [in rounds] one through three, man. I was all over him. It is what it is. I'll get better. I proved that I'm the real deal."
White, watching on, hailed Jones as "the GOAT [greatest of all time], and said he admired how he was finding a way against "these young killers".
But White spared a thought for Reyes, too.
"My kids are terrorising me that the fix is in," he said. "[They are asking:] 'How does this happen, Dad? Reyes won the fight!'
"None of us are judges. The judges call the fight, and that's it."