Billionaire Barry Diller took the stand on Monday to defend his media empire from a lawsuit claiming that it cheated the founders of Tinder out of $2 billion. 

The hookup app’s co-founder and former CEO Sean Rad claims that Diller’s companies — IAC and Match Group — gave outside investment bankers fake “doom-and-gloom” financial projections during a key valuation process in 2017. They say the banks then valued Tinder at $3 billion when it should have been worth at least $13.2 billion, dramatically reducing payouts to the co-founders and other early employees.

Under questioning from Rad’s attorneys, a defiant Diller strongly denied that he ordered subordinates to lie to banks, calling the idea “absurd.” 

“It would be wrong,” said the 79-year-old tycoon in reference to the idea of lying to banks. 

As evidence that Diller allegedly tried to intimidate Rad, Rad’s attorneys pointed to a May 2017 email where Greg Blatt, a longtime Diller ally who succeeded Rad as Tinder CEO, wrote that Diller wanted to “go after” Sean Rad and his family for “everything they have” — in apparent retaliation for the founder complaining about the valuation process. 

The mogul denied trying to menace Rad, saying, “I can kind of conclusively say that I’ve never threatened anyone.”

Blatt himself is scheduled to testify at some point before the trial wraps up in late November or December. The parties could also opt to settle for somewhere from $300 million to $700 million before the trial ends, according to Susquehanna litigation analyst Thomas Claps.

Diller — who wore a striped navy suit and a clear facemask to Manhattan Supreme Court — appeared to grow exasperated with Rad’s attorneys, saying “Oh my god” twice during questioning and dismissing at least one question as “ridiculous.” Rad attorney Orin Snyder and Diller frequently spoke over each other during Diller’s testimony, which lasted more than three hours. 

“Tell me the truth, Mr. Diller,” demanded Snyder, who has also represented Apple, Facebook and WeWork founder Adam Neumann. 

While Diller credited Rad with coming up with Tinder’s iconic swipe-oriented design, he argued that the app likely wouldn’t have reached profitability without years of financial backing and guidance from Match, which also owns dating apps like Hinge and OkCupid. 

“The Match people had become really experts at taking free properties and turning them into businesses,” said Diller, who Forbes estimates is worth a whopping $5.3 billion. “[Match’s] model is literally implanted into Tinder.” 

Rad — who founded Tinder in 2012 while working for a Diller-controlled startup incubator called Hatch Labs — took the stand last week to detail his accusations against Diller’s companies. He said that the contested valuation process — which ultimately netted him nearly $400 million but he claims should’ve given him more than $1 billion — left him with mental scars. 

“I had PTSD, been going to therapy, I’d been working on myself,” Rad said on Friday of his mental state after the 2017 valuation process. 

Rad also said that the experience helped inspire investments he later made in an online health startup.

Another early Tinder employee who is also a plaintiff in Rad’s suit, Alexa Mateen, testified after Diller on Monday, telling jurors that Diller’s companies “cheated us out of what was supposed to be ours, corrupted the valuation.” 

Yet attorneys for Diller’s companies attempted to cast doubt on Alexa Mateen’s testimony when they asked her about a reported $8.8 million that Rad had personally wired to her in late 2017 — less than a year before the group filed the suit against IAC and Match.

Asked about the previously unreported payment, Mateen acknowledged that Rad had sent her the money but said it “had nothing to do with this lawsuit.” 

“Mr. Rad wired me that money because I was one of the first employees at Tinder,” said Mateen, whose brother Justin also worked at Tinder and is a plaintiff in the suit. “I was not happy with the amount of equity I got… he told me not to worry and that he would give me some of his own money.” 

Match attorneys have also used millions of dollars in litigation funding payments to key witnesses to cast doubt on Rad’s case. Rad’s camp has argued that the payments are irrelevant to the suit, and the judge presiding over the trial found that the payments were not illegal, saying that it ”approaches the line between legitimate litigation funding and illegitimate payment of witnesses, [but] it does not cross it.”

Justine Sacco, a spokesperson for Match, claimed that Mateen’s testimony is “not trustworthy” in a statement to The Post. 

“Alexa Mateen, like others, has been paid millions of dollars by Sean Rad’s team,” Sacco said. “Plaintiffs are attempting to corrupt the entire judicial system and we are confident the jury will see through it.”

Rad spokeswoman Brandy Bergman did not respond to requests for comment.