Floyd Mayweather Jr took his boxing record to 50-0 as he stopped Conor McGregor in the 10th round of their fight in Las Vegas.
UFC fighter McGregor caused a surprise by being competitive early in the bout, but Mayweather's class took over as the bout wore on.
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McGregor had promised to take the fight to Mayweather in the pre-fight interviews and the Irishman backed his words up with a strong start, and a number of times he had his more experienced opponent in trouble.
But Mayweather absorbed what McGregor had to offer and referee Robert Byrd had to step in during the 10th round to save McGregor from taking more punishment as the fight became one-sided.
Mayweather told reporters post-fight that McGregor's efforts, in his first competitive boxing match, had earned his respect.
He said: "He is a tough competitor and we gave them what the fans wanted to see - I owed them for the Manny Pacquiao fight.
"He [McGregor] was a lot better than I thought. He was a tough competitor, but I was the better man. Our game plan was to take our time, let him shoot his heavy shots and take him out at the end.
"In the MMA, he fights 25 minutes really hard, and after 25 minutes he starts to slow down. I guaranteed everybody this would not go the distance. Boxing's reputation was on the line."
"This was my last fight tonight, for sure. I chose the right dance partner. Conor McGregor, you are a hell of a champion."
McGregor said: "I took the early rounds pretty handy, he adjusted. He's composed - not that fast or powerful, but boy is he composed and he was making me throw.
"Fair play to him, what a career he's had. I thought it was a little early with the stoppage. I would have liked to have hit the floor, he (the referee) should have let me keep going. I was just a little fatigued. He was a lot more composed under the shots - that's what 50 professional fights will give you.
Meanwhile, a surge in pay-per-view television demand forced a delay to the start of the fight
A statement from Showtime Sports said the start of the fight, due to begin at around 9pm local time had been pushed back.
"Due to high demand, we have reports of scattered outages from various cable and satellite providers and the online offering," Showtime said.
"We will delay the start of the main event slightly to allow for systems to get on track. We do not expect a lengthy delay."
Saturday's fight is tipped to break pay-per-view television records, with some estimates saying it could surpass the 4.6 million buys that Mayweather's 2015 fight with Manny Pacquiao drew.
The Mayweather-Pacquiao fight was also subject to delays as television providers struggled to cope with demand.