Thursday is the 15th anniversary of that epic Forrest Griffin vs. Stephan Bonnar fight that launched the UFC on a multi-billion dollar trajectory.

So, we hit up Forrest to talk about how it changed his life -- and the video is awesome.

Remember, Griffin vs. Bonnar was the main event finale of the very 1st season of the "The Ultimate Fighter" reality show competition -- and it's still widely regarded as one of the best (and most important) moments in MMA history.

Griffin won that 3-round war by unanimous decision and went on to have a Hall of Fame career.

Looking back, Forrest says that night -- April 9, 2005 -- changed his life forever.

"I knew at the end of that I did not have to go to a day job. My job was now professional fighting," Griffin tells us.

"That's the bigger moment than winning the belts or fighting the best guy in the world or anything else. That’s the moment for me that really will always stand out."

Remember, 'TUF: Season 1' was aired the U.S. on Spike TV -- and was it was really the first time UFC content was available to the masses without a paywall.

Dana White has often credited the fight with launching the UFC to the next level -- but Griffin is still humble about his role.

"There were other people who laid the foundation for us and I got to help a little bit too."

"The history of MMA -- so many great people have gotten to offer so much to it, I’m really glad I got to offer my little keystone in it. With all the Chucks and the Royce’s and the GSPs, all the great people that changed the game. The Ronda Rouseys the McGregors, they turned it into a mainstream thing."

Khabib Nurmagomedov's manager ain't happy with Conor McGregor -- blasting him as a coronavirus hypocrite and a "jealous prostitute" after the Irishman criticized Khabib.

"It’s crazy because this guy has been telling people to stay home, don’t come outside, he’s donating millions of dollars, which now we know this sh*t is all fake," Ali Abdelaziz tells us.

Remember, Conor -- who made that emotional plea to Ireland to shelter in place -- accused Khabib of "chickening out" of his April 18 fight against Tony Ferguson.

"Khabib scurried out of the U.S. to home, and amid the crisis," McGregor said.

Well, that didn't sit well with Ali ... who WENT OFF on Conor to TMZ Sports.

"You’re telling everybody to stay home, now Khabib -- the government of Russia says he can’t travel, you’re going to call him a chicken?! [Conor] doesn’t matter."

He continued, "[Conor is not] #1, he’s not #2, he’s not #3. It’s Khabib, Justin, Tony. [Conor is] #4. He’s not even in the conversation right now. He’s just like a jealous prostitute, she’s got too old for her to make money."

Ali also issued this message to McGregor -- "Why don’t you even jump on a plane and come fight Tony Ferguson? I bet he understands that Tony Ferguson would beat his ass too. All those 3 guys would beat his ass. Justin, Tony and Khabib.”

There's more ... Ali also reps Justin Gaethje, who will be fighting Tony Ferguson instead of Khabib at UFC 249 and he told us how that deal came together "within an hour."

As for fighter safety, Ali says Justin and Tony -- and everyone involved UFC 249 -- is in good hands with the UFC.

"UFC for the last 20 years they set a standard about testing medical procedures. There’s never been a death or a serious injury to happen in the UFC."

UFC star Justin Gaethje says he's both excited and terrified about fighting Tony Ferguson at UFC 249 ... saying, "I’m facing my fears right now and I think that’s what we all need to do."

Justin is replacing Khabib Nurmagomedov in the April 18 main event for the interim lightweight title after the COVID-19 pandemic left the Russian unable to leave his home country. White says all fighters on the 249 card will undergo thorough medical screening before being allowed to fight.

The 31-year-old knockout artist says he's never taken a fight on this kind of short notice before -- but explains, "I’ve also never been offered a UFC title and that’s the only thing I’m working for."

"That’s all I’ve been working for since the beginning, so I’m ready to gamble."

So, why did Justin ultimately agree to take the fight?

Gaethje says he didn't immediately say "yes" -- telling his coach he wanted to sleep on it for a night to really think it through.

"The next morning I woke up and said, 'If I lose where are we at?' For me, it’s in the same exact spot I am right now. I’m going to go out there and get a paycheck, which is nice, but ultimately I get a chance at glory."

"Heroes live forever, legends never die and I’m literally here to make a statement. My name will be carried on far longer after I’m here because of my effort, because of my work ethic and because of the skills I possess."

He added, "There’s very few people on earth that would sign up for what me and Tony just signed up for, including most UFC fighters. A lot of guys will say that they’re ready, but a lot of guys would not put their name on the dotted line."

UFC star Anthony Smith -- who's beaten some of the best fighters on the planet -- says he fought off a man who broke into his Nebraska home this weekend ... and, "it was one of the toughest fights I've had in my whole life."

The story is insane ... around 4 AM on Sunday, Smith's wife heard a man in the house "screaming at the top of his lungs."

31-year-old Smith -- who lives in the home with his wife, 3 young daughters (8, 5 and 2)  and mother-in-law -- moved everyone to a room and decided to confront the intruder.

"I'm expecting that I'm gonna hear a gunshot or he's gonna stab me," Smith told ESPN's Ariel Helwani. ... "I figure I've got about two minutes before whatever he's got takes me out."

So, Smith charged hard and tried to subdue the man in his computer room -- but to Anthony's surprise, the man fought back ... HARD.

"No normal human is able to fight like that ... I'm by no means the baddest dude on the planet. But, he's a regular Joe and I had a hard time dealing with him."

"And he took everything that I gave him -- every punch, every knee, every elbow. He took every single one of them and kept fighting me."

During the scrap, Smith says his mother-in-law brought him a kitchen knife to use on the intruder -- but it didn't completely stop the guy.

Eventually, cops arrived and helped to subdue the intruder, identified as Luke Haberman -- who was already bloodied, beaten and cut up.

The craziest part of the story ... Smith says once Haberman was in custody, he apologized -- saying, "Hey man, I'm sorry."

What?!

"I'm not lying when I said it was one of the toughest fights I've had in my whole life," Smith said ... "I went into that fight ready to die."

As for Haberman, he was hospitalized and hit with a citation which requires him to appear in court in the near future.

Smith says the guy had been wreaking havoc in his neighborhood earlier in the night -- and broke into his home through an open garage door.

"I woke up in a guillotine-ish mood."

That's UFC star Brian Ortega explaining why he chose his trademark GUILLOTINE CHOKE as today's lesson for TMZ's Snapchat show "Fight School" ... and the video is awesome!

T-City joined Paige VanZant to train up our TMZ Sports producer, Lucas -- our human crash test dummy -- in the secret MMA gym in the TMZ office!

Not only did Brian drop all sorts of knowledge on us ... but he also let Lucas try out the move ON HIM!!

Did Lucas actually get Brian Ortega -- the #2 ranked UFC featherweight contender -- to tap?!!?

Dana White tells TMZ Sports he's thiiis close to closing a deal to host UFC fights on a private island -- where he would fly in fighters on private planes.

YES, THIS IS REAL!!!

The UFC boss tells us he's laser-focused on keeping the business alive during the COVID-19 pandemic -- starting with UFC 249 on April 18.

White says the location for that event is still top secret -- though he's locked up the mystery venue where it will take place for 2 months and plans on pumping out fights every week.

But, after that, White says he's planning to move the Octagon to the island -- where he will set up shop and host fights involving massive international fighters.

White says the deal for Fight Island isn't done yet -- but it's very close. And, no, we don't know what part of the world it's in.

White also revealed the rest of the card for UFC 249 ... which includes some pretty big fights including Rose Namajunas vs. Jessica Andrade and Francis Ngannou vs. Jairzinho Rozenstruik.

Greg Hardy will also be on the card as well as Ray Borg, Jeremy Stephens and more.

White says every person involved in the fights -- from production staff to fighters -- will be screened thoroughly by a medical team before they will be allowed into the venue. White says safety is the highest priority.

White also talked about Khabib Nurmagomedov -- who was initially slated to fight Tony Ferguson in the main event at UFC 249 until the pandemic left him stuck in Russia. White says people should stop blaming Khabib for being out of the fight, there's nothing he could have done.

It's official ... Justin Gaethje will replace Khabib to fight Tony Ferguson in the main event at UFC 249 on April 18!!!

So, many questions remain -- like where will the event take place -- but so far, that's all we know.

There will be a fight. It will be live on ESPN+. Tony and Justin will fight for the UFC interim lightweight title (Tony previously held it, but was stripped when he injured his leg. Khabib then fought Al Iaquinta for the interim title).

As for the location, Dana White has only teased it will go down "somewhere on EARTH!"

No matter where the fight takes place, the UFC will most likely restrict fans from attending due to the COVID-19 pandemic.

Unclear who will call the fight.

As we previously reported, Khabib Nurmagomedov was all set to fight Tony -- but he's stuck in Russia and unable to fly out.

So, the UFC locked in Gaethje -- one of the most ferocious strikers in all MMA -- to go after Tony instead.

White has said there will be other fights on the card, but he has not revealed the names of anyone else signed on yet.

MMA meets T&A!!

Here's UFC star Paige VanZant and her MMA fighter husband, Austin Vanderford, making the best out of quarantine ... by getting naked and climbing on each other!!

Hey, ya got it? Flaunt it, right?!

Both Paige and Austin have been training their asses off at their Oregon home during the COVID-19 pandemic ... and they've clearly decided the best way to deal with the stress, is to undress!

So, they've basically become nudists in their own home -- they cook naked, the clean naked, the work out naked, they garden naked ... and now they're climbing on each other naked!

Of course, both Paige and Austin are itching for a fight -- Paige recently had her cast removed after suffering a broken arm. She hasn't fought since defeating Rachael Ostovich back in January 2019.

Austin is 9-0 as a pro after locking up another W at Bellator 234 back in November.

Conor McGregor is going after Khabib Nurmagomedov again ... this time blasting The Eagle for "chickening out" of his UFC 249 fight with Tony Ferguson later this month.

"The fact of this matter is, both Tony and Khabib where engaged in a game of chicken here towards the fight bell," The Notorious said Thursday. "With Khabib chickening out first."

Of course, this is the FIFTH time the Khabib-Ferguson fight has been canceled over the years ... and Conor is now deeming Tony the winner after Khabib's latest withdrawal.

"Khab scurried out of the U.S to home, and amid the crisis. Very high risk," McGregor said. "Congrats Tony."

Nurmagomedov clearly ain't laughing at Conor's ribbing ... the UFC star said Wednesday he had legitimate concerns about fighting amid the coronavirus pandemic.

In fact, Khabib expressed frustration over the pressure he's been receiving to fight.

"Famous people around the world urge people to follow all safety requirements in order to limit the spread of the disease," Khabib wrote, "to save people, and Khabib is the only one relieved of all obligations and must demonstrate free will and train flying around the world, for the sake of fight?"

Khabib added that he was super disappointed ... but it ain't like Conor cared.

"I am in shape to fight right now!" McGregor said. "At the beginning of all this, I said to myself -- I’m happy I don’t have an official fight booked."

"If I did, I would have consumed all the incorrect data to support me taking part in the bout, and I would have followed through, competed. And won."

The last time Conor fought Khabib back in 2018, it wasn't even close -- the Dagestani dominated McGregor and ultimately got him to tap out in the 4th round.

UFC superstar Jon Jones has pled guilty to driving while intoxicated stemming from a March 26 arrest in New Mexico, officials tell TMZ Sports.

The reigning UFC light heavyweight champ has struck a deal with prosecutors in which he agreed to 1-year supervised probation. The sentence has not yet been approved by a judge but that's just a matter of time at this point.

As part of the deal, Jones will serve 96 hours in a community custody program -- which is a form of incarceration, but not in a traditional jail cell. We're told it's similar to house arrest. He will wear an ankle monitor, which allows authorities to make sure he doesn't leave his residence unless he has permission.

Officials say Jones will be ordered to "complete a minimum of 90 day out-patient treatment, maximum fines and fees, community service and all other requirements of reporting to probation."

Due to the COVID-19 pandemic, officials are allowing Jones to participate in the outpatient program via video conferencing.

As for the community service, Jones must complete 48 total hours.

Jones must also install an ignition interlock device in any vehicle he operates -- which requires him to complete a breathalyzer (to test for alcohol) before the car will start.

"His attorney and Mr. Jones have been made aware that if he fails to do this, the State will seek to impose the balance of any jail time without regard for any exceptional circumstances," officials say.

Get this ... officials WILL allow Jones to use marijuana during his probation, as long as he has a valid medical card.

As we previously reported, Jones was arrested around 1 AM on March 26 after cops responded to reports of gunfire in the Albuquerque area.

When cops found Jones alone in his Jeep, he appeared intoxicated and admitted to drinking earlier in the evening.

As for the other charges, which include negligent use of a deadly weapon and open containers, those will be dropped in exchange for Jones' guilty plea on the DWI.

Kamaru Usman wants to go all "Deliverance" on Jorge Masvidal at UFC 249 -- saying he wants the fans to hear Masivdal "squeal like the pig that he is."

Both Kamaru and Jorge have said they're down to step up and fight in the main event at UFC 249 in April -- after Khabib Nurmagomedov revealed that he's stuck in Russia and likely won't be able to fight Tony Ferguson.

Masvidal has promised to "cut off" Usman's head if they do scrap -- but Kamaru, the reigning UFC welterweight champ, says he ain't afraid.

In fact, Usman says he LOVES the fact there will likely be no fans allowed at UFC 249 (due to the COVID-19 pandemic) ... because he wants the fans to hear all of the sounds of combat.

"I want you guys to hear him squeal, squeal like a pig, like the little bitch that he is," Usman says.

"The weird sounds that he's gonna make once I'm elbowing and slicing up his face, once I'm dropping hammers on his face. I want you guys to hear that."

"Nobody in the stands no fans to cheer him on so he feels like he's somebody. nobody, just me and him."

"That's why I said I'll take that fight. I haven't been training but I'll take the fight because I wanted you guys to hear what I do to this guy inside."

This is awesome -- UFC star Dominick Reyes teaching us exactly how he landed those CRUSHING uppercuts on Jon Jones ... WELCOME TO FIGHT SCHOOL!!!

Dom hit up the secret gym at the TMZ offices recently -- where he told us straight up, "I definitely won" that fight.

Remember, 30-year-old Reyes took Jones the distance in their Feb. 8 matchup at UFC 247 -- a lot of people think he deserved to win that fight and got screwed on the judge's cards.

So, when Reyes hit up our gym -- he took our resident punching bag, Lucas, to class (with the help of "Fight School" host Paige VanZant!).

Ya gotta watch the whole ep on Snapchat -- Dom shows us how he baited Jones during the fight so he could land those devastating shots.