UFC

Justin Bieber is in a brand new celebrity feud ... with UFC superstar Nate Diaz!!!

Here's the deal ... after the fight, Bieber praised Conor McGregor on social media -- posting a photo of the guy with the caption, "Still the champ."

Then he posted video of a toast he made to Conor saying, "To McGregor. He's still the champ. That broke my heart."

He added, "No bandwagon but Conor is a true champion, fights with style and finesse, all the respect to Nate but his style is terrible. Nate has crazy heart respect."

So, how did Nate Diaz react???

He posted a image on Instagram showing him slapping Bieber in the face with the caption, "Shut your bitch ass up."

He added the caption, "Bieber's a hater."

Your move now, Justin ...

2 Chainz says he ain't throwin' in the towel on Conor McGregor -- saying he wasn't just impressed with the way he fought ... but LOVED the fact he still went clubbin' after the fight.

As we previously reported, Conor hit Surrender nightclub hours after losing to Nate Diaz at UFC 196 -- and then went to a bikini pool party the very next day.

Miesha Tate is questioning Ronda Rousey's focus -- saying Ronda's more worried about having babies than fighting ... and it's going to hurt her when they step in the octagon.

Tate joined the guys on "TMZ Sports" (airs tonight on FS1) -- when we asked her how she felt about fighting Rousey for a 3rd time.

Tate says she's 100% down -- but says she's not sure the feeling is mutual.

"I don't even know what [Ronda] is thinking right now ... it seems like her motivation to stick around was to have Travis Browne's baby. So, I don't know."

Tate was referring to Rousey's interview on "Ellen" -- when she said the only thing that pulled her out of her post-fight funk after the loss to Holly Holm was the thought of starting a family with Browne.

"Every time I've ever lost my motivation is to get back up on the horse and fight someone again and work my way back to the top," Tate says.

There's A LOT more in the full interview which airs tonight at 9 PM PT, 12 AM ET on FS1.

Holly Holm says her loss to Miesha Tate is "not the end for me" -- and has challenged the new champ to a rematch.

Holly went to Instagram and posted a pic of herself in the chokehold that did her in ... saying, "This is how Saturday night ended but it's not the end for me."

"I am going to train hard and show that I am better than this. I am down but not out. Thank you @mieshatate for the opportunity last weekend. Well done. What do you say? ....Let's do this again."

She added the hashtag #downbutnotout.

Conor McGregor and Holly Holm have nothing to be ashamed of -- because they put on two of the greatest MMA fights of all time ... so says Charles Barkley.

Barkley's a big fight fan -- and when we got him out in NYC Monday, he was still raving about UFC 196 and the two big upsets ... Diaz over McGregor and Tate over Holm.

One other thing ... with Miesha beating Holly ... and Holly having beat Ronda ... and Ronda having beat Miesha -- we had to ask Charles if there's one fighter he considers the BEST of the bunch.

Nothing helps to change your mood after a devastating loss like 10 hot chicks at a Vegas bikini party ... just ask Conor McGregor.

Nate Diaz did NOT suffer a hand injury during that violent stand-off with Conor McGregor at the UFC 196 presser Thursday ... with sources telling us Nate is "ready to fight."

After Conor smacked Nate's fist, people noticed Nate clutching his right hand ... and several media outlets speculated that he suffered an injury that could put the fight in jeopardy.

But deeply connected sources tell us, "Nate is fine and ready to fight ... he didn't even see a doctor because he wasn't hurt."

Translation -- the fist escaped unscathed.

IT'S (almost) TIME!!!!

Conor McGregor and Nate Diaz hate each other more then Trump and Rubio ... and now TMZ Sports has even more video that proves how deep the hatred goes.

Check out this raw footage from the UFC 196 news conference ... which shows even more smack talk than you saw on the stage.

Not only does NFL stud Antonio Cromartie know who'll win at UFC 196 between Holly Holm and Miesha Tate ... he knows what the victory dance will be ... saying Holm will twerk to celebrate the win.

Conor McGregor says Nate Diaz owes him a big fat thank you for the paycheck he's about to get for UFC 196 -- and says Nate can even work it off with a few dances.

Conor avoided any racial slurs during Thursday's pre-fight news conference in Las Vegas, but still blasted Diaz ... calling him a "scared little boy" who has a "bully mentality until a real man shows up."

Check out the video, 'cause things really got intense when they started talking money and Conor said, "Dance for me, Nate! And don't look me in the eye!"

Former UFC star Kenny Florian thinks Conor McGregor might just be the greatest of all time ... at talking smack ... saying the Irish swagmaster is the best with his mouth since Muhammad Ali.

Johnny Manziel is bringing the party train to Vegas this weekend -- at least, that's the plan ... 'cause his name has popped up on the celebrity guest list for UFC 196, TMZ Sports has learned.

This is actually pretty funny ...

Nate Diaz was doing a Twitter Q&A with fans to promote UFC 196 -- when he was asked to name his 5 favorite rappers of all time.

He could only get to 4 ...

So, naturally ... the next fan asked if he was high on drugs.

Tough guy respects tough guy.

Vinnie Jones says when it comes to UFC fighters, he's all about Conor McGregor.

Vinnie joins a huge list of celeb McGregor supporters -- one that already includes Shaq, Arnold Schwarzenegger, U2's The Edge, Gordon Ramsay and many many more.

It'll be interesting to see if Nate Diaz can rally up some celeb support before the two do battle at UFC 196 this weekend.

One thing's for sure ... Nate's bandwagon will certainly fill up if he wins.

Ooops.

Most UFC fighters would be PUMPED to be on 'Kimmel' -- but not UFC fighter Jake Ellenberger ... who got caught in a big time lie during a political bit on the show Tuesday night.

Kimmel was doing his "Lie Witness News" segment -- where he goes out to bust people lying about voting on Super Tuesday.

The setup -- there was NO presidential voting in California yesterday ... but Jimmy sent a reporter to ask people if they voted to see if they would lie about it on camera to make themselves look good.

Ellenberger fell for it ... hook, line & sinker.

Ooops.

Conor McGregor rolled into a megafan's L.A. apartment this week -- after seeing a cardboard cutout of himself on the guy's balcony ... and the fan was so blown away, he could barely hold himself together.

Conor was driving to the gym when he noticed the cutout (which was displayed along with an Irish flag) -- and screamed up to the guy that he would drop in.

What ensues is pretty awesome ... you gotta watch the clip.

As for Conor's opponent at UFC 196 (which goes down March 5th in Vegas) -- we also got video of Nate Diaz in a recent training session ... acknowledging that he might get "merked."

It's pretty revealing footage ... Diaz knows McGregor is a dangerous guy -- but warns Conor not to underestimate him.

One last thing ... check out this video of McGregor hitting up Rodeo Drive in Bev Hills after tooling around in his Lambo -- dude LOVES to be rich!!!

Watch UFC 196 – McGregor vs. Diaz – Live on PPV on Saturday, March 5.