An American boxer scored a KO of the month when he hit his opponent so hard the mouthpiece flew out of the ring

• An American boxer called Rowdy Legend Montgomery scored one of the KOs of the month.
• The 35-year-old wailed fists onto his opponent, finishing Martez McGregor with a right hand.

An American boxer called Rowdy Legend Montgomery scored one of the knockouts of the month when he hit his opponent so hard the mouthpiece flew out of the ring.

The 35-year-old was competing against Martez McGregor midway through a six-bout Top Rank event at the Virgin Hotels in Las Vegas, and almost stole the show with his thudding finish.

Montgomery wailed fists onto McGregor and, in the finishing sequence early in the third round, hit him with a hard right hand.

Though the referee began the count when McGregor had hit the deck, there was really no need to continue. McGregor's eyes were rolling around his head, he had little control over his body, and the fight was over.

Montgomery had won.

Watch the finish right here:

With the win, Montgomery advanced his pro boxing record to seven wins (five knockouts) against three losses and a draw.

In the main event of the evening, the fast-rising women's super featherweight boxing champion Mikaela Mayer continued to generate more fame with a strong win over the more experienced Maiva Hamadouche.

Bob Arum, Top Rank founder and CEO, was elated with Mayer's performance.

"This was a sensational fight, one of the best fights of the year, male or female," he said in a statement sent to Insider.

"These two ladies are a credit to the sport, and they left it all in the ring. It was a close fight, but I felt Mikaela did more than enough to have her hand raised."