The day after Elon Musk challenged Mark Zuckerberg on social media to “a cage match” last month, Dana White, president of the Ultimate Fighting Championship, received a text.

It was from Mr. Zuckerberg, chief executive of Meta. He asked Mr. White, who heads the world’s premier mixed martial arts competition, which is fought in cage-like rings, if Mr. Musk was serious about a fight.

Mr. White called Mr. Musk, who runs Tesla, Twitter and SpaceX, and confirmed that he was willing to throw down. Mr. White then relayed that to Mr. Zuckerberg. In response, Mr. Zuckerberg posted on Instagram: “Send Me Location,” a reference to the catchphrase of Khabib Nurmagomedov, one of the U.F.C.’s most decorated athletes.

Since then, Mr. White said, he has talked to the tech billionaires separately every night to organize the showdown. On Tuesday, he said, he was “on the phone with those two until 12:45 in the morning.” He added, “They both want to do it.”

If you thought that a cage fight between two of the world’s richest men was just a far-fetched social media stunt, think again.

Over the past 10 days, Mr. White said he, Mr. Musk and Mr. Zuckerberg — aided by advisers — have negotiated behind the scenes and are inching toward physical combat. While there are no guarantees a match will happen, the broad contours of an event are taking shape, said Mr. White and three people with knowledge of the discussions.

The fight would be an exhibition match, Mr. White said, and outside official U.F.C. jurisdiction and rights deals, though he would help produce the event. The tech leaders have agreed there should be a charity component, Mr. White and a person familiar with the talks said, with details still being worked out. The preferred location is Las Vegas, which requires approval from the Nevada Athletic Commission. On Thursday, Mr. Musk tweeted that the event could also happen in the Roman Colosseum.

Mr. Zuckerberg’s friends and advisers have generally supported the match, two people close to him said, though others said a fight would be a distraction and not the best use of his time. One person close to Mr. Musk said that while he hated sports and didn’t appear to have the discipline to train regularly, no one could rule anything out with him.

If the matchup between Mr. Musk, 52, and Mr. Zuckerberg, 39, goes ahead, it would be a rare spectacle, even in the braggadocio-filled universe of the tech industry. While Steve Jobs and Bill Gates used to snipe at each other, the closest the tech world had before this to real sporting feuds was among billionaire yachtsmen like Larry Ellison of Oracle and Hasso Plattner of SAP.

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Apple. The Justice Department joined 16 states and the District of Columbia in filing a lawsuit against Apple, arguing that it had violated antitrust laws with practices that were intended to keep customers reliant on their iPhones by preventing other companies from offering applications that compete with Apple products.

Amazon. The Federal Trade Commission and 17 states have sued the e-commerce giant, accusing it of protecting a monopoly over swaths of online retail by squeezing merchants and favoring its own services. The outcome could alter the way Americans shop online.

Meta. The Federal Trade Commission and more than 40 states have accused Facebook of buying up its rivals, particularly Instagram in 2012 and WhatsApp two years later, to illegally squash competition that could have one day challenged the company’s dominance. They have called for the deals to be unwound.

Google. The Justice Department has targeted the tech giant with two separate lawsuits. In 2020, the agency accused Google of illegally protecting its monopoly over search and search advertising. In 2023, the Justice Department and a group of eight states accused it of illegally abusing a monopoly over the technology that powers online advertising.

But two wildly wealthy tech titans grappling, punching and kicking in a Las Vegas or Roman arena? No one would have dreamed it.

Meta declined to comment. Mr. Musk did not respond to a request for comment.

Mr. Zuckerberg and Mr. Musk have long teetered between being competitors, frenemies and outright enemies. The two have criticized each other over the years, including about Mr. Musk’s SpaceX rockets, data privacy scandals at Meta and more. Most recently, Mr. Zuckerberg dispatched a team at Meta to build a competitor to Mr. Musk’s Twitter, code-named Project 92.

If they take their rivalry beyond those jibes, the U.F.C.’s Mr. White said he had concerns about the physical gaps between the billionaires. Apart from their 13-year age difference, Mr. Musk is said to be at least 70 pounds heavier than Mr. Zuckerberg. In official mixed martial arts bouts, athletes are generally matched up by weight.

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“We have two guys that have never professionally fought, and they’re in two completely different weight classes,” Mr. White said. Still, he said, “it will be the biggest fight in the history of combat sports.”

Mr. Zuckerberg is especially familiar with the U.F.C. world. Over the past 18 months, he has embarked on a personal journey to bulk up and dove deep into Brazilian jujitsu, a grappling martial art in which competitors try to submit their opponent and which is used in U.F.C. fighting.

Mr. Zuckerberg started training on a lark mostly in his garage in 2021, where he built what he called a “mini academy” with a circle of friends who spar with him. He has said he appreciated that Brazilian jujitsu required “100 percent focus” and strategic thinking to defeat an opponent, rather than brute strength.

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• Apple: The company said sales fell 4%, as revenue from iPhones, iPads and wearables like the Apple Watch declined. Apple’s struggles were most worrisome in China, the world’s second-largest smartphone market, where sales fell 8 percent.
• Alphabet’s Revenue Jump: Google’s parent company reported strong revenue growth in its latest quarter from its search engine and video platform, YouTube, as its market-leading position in online advertising continued to reap rewards despite recent industry fluctuations.
• Tech Law Logjam: For years, federal lawmakers have tried to pass legislation to rein in the tech giants. The TikTok law was their first success. Can it be repeated?
• Silicon Valley Worth: Andreas Bechtolsheim, the first investor in Google, has an estimated $16 billion fortune. He recently settled charges that he engaged in insider trading for a profit of $415,726.

Mr. Zuckerberg has sought out martial arts experts, including Dave Camarillo, James Terry and Khai Wu. In May, he competed in his first public martial arts tournament in Redwood City, Calif., which he attended undercover — up until the moment he took off his hat and sunglasses to fight. He won gold and silver medals in the challenge.

Last year, Meta also announced it had partnered with the U.F.C. to bring mixed martial arts fights to Horizon Worlds, its virtual reality app.

Mr. White said Mr. Zuckerberg was truly dedicated to the sport.

“I’ve been talking to Zuckerberg now for maybe close to two years now,” he said. “And there’s never like banter or we’re joking and laughing.” He said the Meta chief executive was “dead serious all the time.”

Mr. Zuckerberg is likely in fighting shape. He has been on a strict workout regimen, going for runs and challenging friends and colleagues to beat his times, two people close to him said. Last month, he posted a personal record for completing the “Murph” challenge, which requires completing a series of pull-ups, push-ups, running multiple miles and doing hundreds of squats, all while wearing weighted, military-grade body armor.

“Doing sports that basically require your full attention, I think, is really important to my mental health and the way to stay focused on everything I’m doing,” he said in a recent podcast episode.

Mr. Musk, on the other hand, has tweeted that he “almost never” works out and once suffered a back injury that required surgery after participating in an exhibition with a sumo wrestler. Last month, he said he had trained in “judo, Kyokushin (full contact)” — two Japanese martial arts — and “no rules streetfighting.”

“He made that very clear: ‘I’m not going to lose any weight,’” Mr. White said of Mr. Musk’s approach to the potential matchup. “‘Are we going to fight or are we not going to fight?’” Mr. White said Mr. Musk told him.