Elon Musk challenges Johnny Depp to 'cage fight' over Amber Heard affair rumours

Tesla mogul Elon Musk has denied having an affair with Amber Heard behind her ex-husband Johnny Depp's back.

Musk also jokingly challenged Depp to a "cage fight" for threatening to cut off his manhood, according to the New York Post.

"I definitely was not having an affair with Amber while she was married to Johnny, this is totally false," Musk, 49, told the New York Times in response to cheating claims made during Depp's UK libel trial.

The father of six laughed at claims he had a threesome with Heard, 34, and model Cara Delevingne, 27, in Depp's Los Angeles penthouse.

"We did not have the threesome, you know. So I think people think these things are generally more salacious than they are."

He also insisted that he only started dating Heard after she split from Depp, suggesting that the pair should "bury the hatchet and move on".

Elon Musk has laughed off claims he had an affair with Amber Heard behind Johnny Depp's back. Photo / Getty Images

Musk, who according to Forbes is worth over $66 billion, laughed again when the Times asked him to comment after Depp called him "Mollusk" in court.

"Well, yeah, I hope he recovers from this situation," Musk said.

And when asked about text messages Depp allegedly sent him, threatening to "slice off his d**k", Musk said, "If Johnny wants a cage fight, just let me know."

Musk said his current partner Grimes, who recently gave birth to their son X Æ A-Xii, is "pretty special".

Musk said Depp was welcome to face him in a "cage fight". Photo / Getty Images

"She's one of the most unusual people I've ever met," he said.

"We've had this debate of 'Are you more crazy than me or am I more crazy than you?'"

The 32-year-old singer, whose real name is Claire Boucher, "has a much bigger role" in parenting than he does because "babies are just eating and pooping machines", Musk said.

"Right now there's not much I can do … When the kid gets older, there will be more of a role for me."