FIGHTIN’ WORDS

Elon Musk has denied sleeping with Amber Heard behind Johnny Depp’s back — jokingly challenging the Hollywood star to a “cage fight” for threatening to cut off his manhood, a report said.

“I definitely was not having an affair with Amber while she was married to Johnny. This is totally false,” the Tesla mogul told The New York Times, responding to claims made during Depp’s explosive libel trial in London.

Musk, a 49-year-old father of six, laughed when asked about other claims in legal documents that he had a threesome with Heard, 34, and the model/actress Cara Delevingne, 27, in Depp’s Los Angeles penthouse.

“We did not have the threesome, you know,” he told the Times. “So I think people think these things are generally more salacious than they are.”

Insisting he started dating now-ex Heard only after she split from Depp, Musk suggested during an hourlong phone interview that the warring exes “bury the hatchet and move on.”

Musk — who is worth more than $66 billion, according to Forbes — again chuckled when the Times asked about court revelations that Depp had dubbed him “Mollusk” in a slur against his suspected love rival.

“Well, yeah, I hope he recovers from this situation,” Musk told the newspaper.

He had a far more unexpected response when asked about text messages the “Pirates of the Caribbean” star had sent allegedly threatening to “slice” off the mogul’s “d- -k.”

“If Johnny wants a cage fight, just let me know,” Musk told the Times, again giggling.

Musk called current partner Grimes — who recently gave birth to their son, X AE A-Xii — “pretty special.”

“She’s one of the most unusual people I’ve ever met,” he said of the 32-year-old singer, whose real name is Claire Boucher.

“We’ve had this debate of ‘Are you more crazy than me or am I more crazy than you?’ ”

The singer “has a much bigger role” raising their son because “babies are just eating and pooping machines,” Musk told the Times.

“Right now there’s not much I can do . . . When the kid gets older, there will be more of a role for me,” he said.

Depp’s case against the UK’s Sun newspaper is expected to wrap this week after three weeks.

He is suing the newspaper for calling him a “wife beater” — based on claims made by Heard. Depp has denied ever assaulting the actress, instead testifying in court that she was the aggressor in the relationship.