Justin Bieber enters the boxing ring - and you may have heard of the other guy

Justin Bieber has finally found an appropriate activity to do shirtless.

The 20-year-old singer hopped in the ring with Floyd Mayweather for some boxing lessons on Thursday night.

"Training with the Champ @FloydMayweather tonight," the Biebs casually posted on his Vine account.

The short clip showed the undefeated boxer holding up some pads for the pop star to swing at. Floyd even gave his pal a nickname… "money bags."

Adorable.

 "Training and having a good time with @justinbieber," the 37-year-old tweeted after the lesson.

In May, the "Confident" crooner (and Lil Wayne) escorted Mayweather to the ring for his fight against Marcos Maidana.

Bieber is frequently seen at Floyd's boxing matches with their friendship dating back to 2012. Apparently, Floyd's daughter is a fan of the singer.

Mayweather's former pal 50 Cent actually explained the Justin-Floyd connection to MTV two years ago.

"Justin is also a Floyd fan," the rapper revealed.

"They love the sport. A lot of people like it and haven’t actually made contact or received anything to make them feel like it was cool or comfortable enough for them to come.

“When it actually happens and it goes down like that, it feels good. When they get a chance to see different genres, different people, everybody's excited. Floyd's daughter, Yaya, she saw half the fight, the other half she was looking at Bieber."

Fourteen-year-old Iyana's Twitter avatar is even a photo of her and Justin.

It’s a happier sparring story involving Mayweather than one covered by Yahoo Sports US boxing writer Kevin Iole yesterday, which reports legal action against the pound-for-pound pugilistic king.

The sons of former heavyweight champion Hasim Rahman have sued Mayweather Jr., Mayweather Promotions and Showtime in Clark County District Court regarding sparring sessions at Mayweather's gym that were a part of the "All Access" series.

Hasim Rahman Jr., 23, and Sharif Rahman, 18, sued for battery, tortious assault, false imprisonment, negligent hiring, training, supervision and retention and unjust enrichment. Neither Rahman has fought professionally, though Rahman Jr. is scheduled to turn professional on Nov. 13.

The Rahman brothers both sparred British boxer Donovan Cameron at the Mayweather Boxing Club in Las Vegas during Episode 2 of Showtime's "All Access" series that was broadcast on Sept. 6 and designed to promote Mayweather's rematch on Sept. 13 against Marcos Maidana.

Mayweather referred to the gym as the "dog house" on the episode.

"Guys fight to the death," a grinning Mayweather says during the Sept. 6 episode. "It's not right, but it's dog house rules."

But Mayweather testified in front of the Nevada Athletic Commission on Sept. 23 that much of what was shown during the "All Access" series was false, made up to help boost pay-per-view sales.

The commission subpoenaed Mayweather to appear after Showtime aired footage of what was alleged to be a continuous 31-minute round. Mayweather told the commission there were numerous breaks in the 31-minute round, though he was not put under oath facing penalty of perjury that day.

The Rahmans' suit, though, disputes that and alleges there was indeed a 31-minute sparring session. There are numerous video interviews with Rahman Jr. on YouTube and other Internet sites in which Rahman Jr. insists he sparred 31 minutes continuously against Cameron.

The suit also accuses the Mayweather Boxing Club of not having the proper license to allow amateurs to spar.