Floyd Mayweather Jr triumphed in his grudge match against Conor McGregor with a 10th-round stoppage in Las Vegas to rack up a record-breaking 50th career victory after an exhilarating contest.

In a bout that completely defied the pre-fight predictions of an easy Mayweather victory, the American showed his class as the rounds progressed to earn the bragging rights at the T-Mobile Arena.

Many had predicted that UFC star McGregor would be out of his depth against one of boxing's all-time pound-for-pound kings on his professional debut in the squared circle.

But the Irishman looked accustomed in the ring early in the contest and clearly had Mayweather confused with his unorthodox, wily style and there were signs that the mother of all upsets was on the cards.

However, as so often during his career, Mayweather's boxing nous came to the fore and he found his range, pouncing on a tiring opponent to land a flurry of blows in the ninth and a similar pattern in the following stanza brought an end to the contest one minute and five seconds into the round.

Mayweather consequently protected his reputation and legacy to beat Rocky Marciano's record of 49-0, but McGregor can take heart from a performance that went against the predictions of boxing pundits around the world.

McGregor was the busier fighter from the off, landing a couple of left-hand counters in round one and switching stances to confuse Mayweather.

The American was visibly uncomfortable with McGregor's full-throttle style and swift combinations in the second were followed up in the third with successful jabs through the guard.

But the momentum began to swing in Mayweather's favour as the fight burst into life in the fourth, a couple of feisty exchanges were followed by the 40-year-old landing a flush left and following up with a stiff shot to the body.

Mayweather pressed home as McGregor was clearly tiring, finding his range with the overhand right as his opponent struggled to keep pace.

Bizarre scenes occurred in round six as McGregor was allowed to continue throwing punches with Mayweather's back turned, but 'The Notorious' took a right straight to the chin and his power was dwindling.

McGregor's work was tidy enough but his shots were tame as Mayweather landed a straight right and followed up with a well-executed screw shot.

By the ninth, McGregor was fighting on tiring legs and staggering around the ring as Mayweather landed with left and rights and the UFC star did well to make the bell.

But it only delayed what was quickly becoming the inevitable and as Mayweather unloaded with more big shots in the 10th, forcing McGregor onto the ropes, the fight was brought to a thrilling end.