UFC

Secret's out ... Demi Lovato is dating UFC superstar Luke Rockhold -- and TMZ Sports has learned it's a romance that's been blooming for a couple months.

Our sources tell us ... the 24-year-old singer hit it off with the 31-year-old former UFC middleweight champ earlier this year while training at Unbreakable gym in Los Angeles.

Long story short ... we're told the two clicked right away -- and have even sent some secret inside messages to each other on social media ... including a back and forth with smiley face art on their fingers.

Congrats!

Jennifer Lopez broke up with Casper Smart because he snubbed her by passing on a fancy Hamptons charity event in favor of hanging with his boyz at UFC 202 ... TMZ has learned.

Sources connected with the former couple tell us ... J Lo told Casper it was super important for him to accompany her to Ron Perelman's Hamptons fundraiser Saturday night benefiting the Apollo Theater.

Casper wasn't having it, because he desperately wanted to watch the Conor McGregor/Nate Diaz fight in Vegas with his friends.

Casper had a great time in Vegas, hanging with Kanye and UFC announcer Bruce Buffer.

J Lo, we're told, was enraged and ended the relationship ... no discussion -- simply, we're done.

Here's the funny thing ... Casper was telling people at the fight he was going to NYC Sunday to meet up with Jennifer, who was there filming a show. He had no idea being a no-show Saturday would end things.

Our sources add this ... J Lo and Casper have "broken up" several times before and gotten back together, and they say they would not be surprised at all if it happens again.

J Lo doesn't look like she's too broken up about it at the moment, though ... she was still in New York this morning looking perky as ever.

Nick Diaz ended up in the middle of a huge brawl while partying at Hyde nightclub in Vegas early Wednesday morning ... TMZ Sports has learned.

A rep for the club tells us the UFC fighter went to a bathroom outside the club around 2:30 AM, and accidentally stumbled into another customer ... who started talking smack.

UFC superstar Paige VanZant says she's on such good terms with Ronda Rousey after their heated encounter earlier this year ... she's decided to read her book ... and LIKES IT.

As we previously reported, Rousey confronted Paige at an event in L.A. back in April -- and cussed her out for congratulating Holly Holm on her victory at UFC 197.

VanZant says it's all water under the bridge -- "we're cool actually" -- and says she's learning a lot about Rousey in her book, "My Fight/Your Fight."

"It's really good and it's cool to kinda get inside and see the things that she's gone through that are similar to me," Paige said ... "So yeah ... no worries there."

Paige is gearing up to fight Bec Rawlings at UFC Fight Night in Vancouver on Saturday -- and essentially guarantees victory.

What happens when you get to your cageside seats at UFC 202 -- and Mike Tyson's sitting in 'em???

That's the question Kanye West had to ask himself when that happened to him at the Conor McGregor vs. Nate Diaz fight in Vegas this past weekend.

FS1's Skip Bayless says he saw the entire thing go down -- because he was sitting right behind Kanye's reserved seats.

But what transpired wasn't a fistfight ... one of the stars backed off in a big way -- and it wasn't who you think it would be.

Nate Diaz gave an upstart vape pen company a HUGE BOOST when he lit up after UFC 202, and now the biz is struggling to meet the high demand.

Tru Vape Oil's founder, Derek Hodslo, says his phone and computer haven't stopped blowin' up since Nate puffed on one of his pens at Saturday night's news conference. He says the endorsement was totally unplanned and, in fact, Nate caught 'em off guard.

He says they had no time to stock up on the cannabidiol (CBD oil) which Nate was using that night -- and also shouted out on Instagram. Hodslo estimates they could've shipped 20,000 units, but they only had 506 CBD cartridges in stock.

Still, he says the publicity is invaluable and will eventually pay off -- even if they're not getting rich quick.

As for Nate catching heat from USADA for smoking CBD -- he says it helps him deal with post-fight inflammation -- Hodslo is team Diaz all the way, standing by his product's healing properties.

It's a good thing Michael Bisping can multitask ... 'cause the UFC middleweight champ says he'll be training for his next fight against Dan Henderson while shooting his new movie in London.

Bisping locked up a role in the bare-knuckle boxing flick, "My Name Is Lenny" -- which starts filming this week. Bisping says his part will take roughly 2 weeks to complete.

But he also has a huge fight coming up against Hendo at UFC 204 in October -- just 7 weeks away.

So, how will he be able to prep for the fight and shoot the flick?

"My trainer's gonna come with me. I'm still gonna train every day. Film the movie. Come back. Focus on the fight. Kick some ass."

FYI, other fighters like Paige VanZant and Conor McGregor have turned down roles to focus on training camp -- but clearly, Bisping thinks he can handle both.

Sorry, Matt Barnes ... LeBron James would beat that ass in a street fight -- so says someone who would know, UFC tough guy Brad Tavares.

Tavares was chillin' at Sake Rok in Vegas for the UFC 202 fight when he admitted he's not really a Bron fan -- but knows what the guy could be capable of if he truly trained for a real deal fight.

Fun fact -- Tavares is fighting in LeBron's home state at UFC 203 next month.

It was an Irish megastar explosion after UFC 202 -- with Rory McIlroy and Niall Horan congratulating Conor McGregor at the post-fight party ... and TMZ Sports has the video.

It all went down at Intrigue Nightclub -- where the Irish golfer and the Irish boy-bander approached the Irish fighter to revel in their full Irish awesomeness.

NBA star Dwight Howard is a huge UFC fan -- so when we got him leaving UFC 202, we had to ask ... who would win if you stepped into the Octagon with LeBron James??

Howard ain't no bitch -- and says he'd put his money on himself.

Look, he was just joking around ... but let's check out the tale of the tape:

Dwight -- 30 years old, 6'11", 265 lbs with a wingspan of 7'4".

LeBron -- 31 years old, 6'8", 250 lbs with a wingspan of 7'0".

So, who YOU got???

Check out the clip ... Howard also says he's a big WWE fan and would be down to follow Dennis Rodman's lead and do a little wrastlin' himself at some point.

"I'll get out there and scream and yell and suplex sombody! RKO outta nowhere!"

The $300,000 Conor McGregor shelled out for his training camp -- on everything from masseuses, to nutritionists and Diaz-alike sparring partners -- was WORTH IT ... so says Forrest Griffin.

Remember, Conor said he was sparing no expense to avenge his loss to Nate Diaz -- and told ESPN he was blowing out the budget to make his camp the best training experience money could buy.

Well, when we saw Griffin after UFC 202 -- he told us the results speak for themselves.

Like Conor McGregor was gonna miss a victory party?

Here's video of The Notorious heading into Encore Beach Club at the Wynn on Sunday -- one day after beating Nate Diaz in one of the craziest UFC fights we've ever seen.

Conor didn't look too bruised up ... but he did enter the party with a pretty obvious limp.

McGregor insists he did NOT break his foot -- but banged up his shin during repeated strikes to Diaz during the UFC 202 fight.

Still, he didn't let the pain keep from partying with all the bikini-clad chicks at the club!

Congrats!

It's as shocking as Saturday night's fight was awesome ... there will be no Conor McGregor and Nate Diaz trilogy ... according to the man who makes the decision.

Dana White tells TMZ Sports he wants Conor to defend his title against interim champ Jose Aldo. Dana says, "The war was fun and super successful but I'm movin' on." Here's the rub -- Conor beefed up for his fight against the much larger Diaz. Conor normally fights at 145 and swelled to 168 to fight Diaz.

Dana says Conor has two options -- either fight Aldo or surrender his title to him -- or cut weight to 155 and fight Eddie Alvarez for the lightweight title.

Dana says under any scenario, he's closing the books on McGregor vs. Diaz.

Conor McGregor celebrated his win against Nate Diaz in what UFC aficionados are calling a fight for the ages.

Conor cut loose at Intrigue Nightclub in Vegas, after beating Nate by majority decision.

The fight went back and forth all 5 rounds, but Conor eked out the win.

Niall Horan from One Direction -- a fellow Irishman who predicted Conor would win by submission in the 3rd -- showed up for the bash with his GF. Conor's girlfriend, Dee Devlin, was also front and center.

Jon Jones is ALMOST out of Dana White's doghouse ... with the UFC honcho telling TMZ Sports he doesn't believe the ex-champ was using steroids ... but he did take SOMETHING he shouldn't have.

White joined the guys on the "TMZ Sports" TV show (weeknights on FS1) -- and spelled out the latest with Jones and the failed drug tests that got him kicked off the card at UFC 200.

"He was accused of taking the drug that you take when you're getting off steroids ... and it's looking now like it's not the case. He did not take that drug. He took something else that had it in it."

White says he's not as pissed off at Jones as he was in the wake of the failed test -- but he's still upset.

"I'm a little happier now that he wasn't taking that drug and that I now believe that he wasn't taking steroids ... but still, you can't put anything in your body without notifying USADA or the Nevada State Athletic Commission."

Here's proof Conor McGregor still has HUGE support in the WWE ... Big Show saying despite CM's vicious diss of the whole organization ... he's still a fan of the Irish hell-raiser.

We got Big Show out in NYC and asked what his response was to Conor dissing the entire organization ... calling them a bunch of "messed up p***ies."

Other wrestling legends like Ric Flair came out HARD against McGregor but Big Show played the big diplomat ... singing CM's praises, and not ruling out a future WWE stint for the UFC king.