Floyd Mayweather won for the 50th time in his decorated career when the fantasy fight with Conor McGregor proved a mismatch and he stopped the Irishman in 10 rounds in Las Vegas.
The American has long vowed this would be his final fight, but even at the age of 40 and after almost two years of inactivity he showed few signs of decline in outclassing McGregor, who was making his professional debut at the T-Mobile Arena.
McGregor's greatest chance of success came in using his superior size and weight - he was 3.5lbs heavier at Friday's weigh-in and bigger still in the ring - to smother Mayweather.
McGregor landed a reasonable left uppercut in the opening round as Mayweather analysed his opponent who repeatedly switched his stance.
A recurring theme throughout the fight began in the second round, when referee Robert Byrd had to warn McGregor for punching behind the head. Mayweather's defence nullified any potential sting in the Irishman's punches and then he responded with two sharp right hands of his own.
McGregor's renewed aggression at the start of the fourth was swiftly turned against him as Mayweather began to read him, landing another big right on the counter after ensuring another remained out of range.
In the sixth-round Mayweather was turned and McGregor again went without punishment for punching behind the head, but by its conclusion he was showing significant signs of fatigue and unravelling amid a number of further right hands.
Any respect the American may have had for his opponent's threat disappeared at the same rate McGregor tired, his sense of distance ensuring the biggest question became how long the 29-year-old would survive.
A low blow in the ninth on Mayweather also went unpunished, but he then similarly took advantage of McGregor's lack of form to continue landing with the jab and right to leave him desperately clinging on.
The inevitable conclusion followed in the 10th round when, with the stumbling McGregor unable to avoid Mayweather's sharp accurate right hands, Byrd finally showed some conviction to rescue the resilient Irishman and wave the action over after one minute and five seconds.
With the victory, Mayweather's record surpassed that of the great Rocky Marciano by improving to 50-0
Conor McGregor's debut bout in the boxing ring may not be his last as following the defeat the Irishman said:
"anyone who wants a knock, give me a shout."