Floyd Mayweather extended his perfect career record to 50 fights unbeaten by stopping Conor McGregor in the 10th round of one of the richest bouts in boxing history.
The former five-weight world champion faced flurries of early punches from UFC's most iconic figure, who was making his debut in professional boxing at Las Vegas' T-Mobile Arena.
McGregor delivered a crisp uppercut in round one and, though he edged close to breaking the rules with several punches to the back of the head, he imposed himself admirably without ever looking as though he would knock out Mayweather.
The American, who came out of retirement for a potential $300m (£230m) pay day, executed a gameplan which pounced on McGregor's lack of conditioning for the late rounds which prove so key on big fight nights.
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As the Irishman tired, Mayweather upped his ferocity and by round nine the 40-year-old began to stalk his opponent, whose legs were weakening under more successful shots.
And in the 10th, with McGregor again near the ropes and offering little, the fight - which followed weeks of manic build-up, spiteful words and chaos - was over. He was not bowled over by a conclusive blow, but with Mayweather throwing rapidly, his target was left too vulnerable.
Referee Robert Byrd's stoppage may have arrived too early for some, as McGregor's early effort led to a belief inside the arena he could pull off the biggest upset in the history of the sport.
But the 29-year-old was wilting and was down 89-81 89-82 87-83 on the ringside cards when the stoppage came.
His effort and display should be commended, but Mayweather's poise and invincibility remain constant into retirement.
Mayweather said: "He was a lot better than I thought. But I was the better man. I guaranteed everybody this would not go the distance. Boxing's reputation was on the line."
McGregor, who said he would return to the UFC but would not rule out boxing again, said: "I thought it was close and I thought it was a bit of an early stoppage. I was just a little fatigued."
Watch highlights of the final round below;
Watch the full fight below;