The 'X Factor' judge, who famously created One Direction in 2010, vouches for Styles' character in a late-night.
The talent judge, who has long been a champion of Styles and famously put the boys of One Direction together on The X Factor in 2010, gushed over the singer's character when asked about the recent spitgate drama out of the Venice Film Festival.
Days ago, Styles started an internet frenzy when footage appeared to show him spitting on his Don't Worry Darling co-star Chris Pine at the premiere of their film. Styles later joked about the alleged incident during a performance at Madison Square Garden, while Pine's rep vehemently denied it happening.
"That doesn't sound like Harry," Cowell said on Thursday in an appearance on Jimmy Kimmel Live.
Host Jimmy Kimmel noted that maybe Styles spit on "accident."
"I was thinking that, yeah," Cowell admitted. "You know when you gob on someone by accident -- you go, 'Oh, I'm really sorry I did that.'"
"He definitely, definitely wouldn't do that," Cowell continued. "That's not Harry. Harry's very polite and charming. He wouldn't do that."
He added, "I would tell you! He's a very, very, very nice guy."
On Wednesday, Styles resumed his Madison Square Garden residency in New York and addressed the controversy.
"I just popped very quickly to Venice to spit on Chris Pine," the 28-year-old singer joked before breaking out in a fit of laughter.
"But fret not, we're back," he told the sold-out crowd, before launching into his next song.
While the incident had become the talk of the festival, Pine's rep denied that it happened.
"This is a ridiculous story -- a complete fabrication and the result of an odd online illusion that is clearly deceiving and allows for foolish speculation. Just to be clear, Harry Styles did not spit on Chris Pine," the rep told ET. "There is nothing but respect between these two men and any suggestion otherwise is a blatant attempt to create drama that simply does not exist."
Cowell's appearance on Kimmel came on the same day as Queen Elizabeth II's death. Both Styles and Cowell paid tribute to the queen that evening, with Styles leading the crowd at his concert in a round of applause for the late monarch. For his part, Cowell recalled the time he met Queen Elizabeth at a TV taping in the U.K.
"This was the British version of Got Talent and the winner of that show gets to perform in front of the royal family on a different show, called The Royal Variety Show," Cowell said. "And that night the Queen was there, so I went along and fortunately got to meet her backstage. I mean, it was amazing."
Cowell recalled with a laugh, "She didn't talk to me. She had no idea who I was, actually."
" I was kinda like in awe, because you're told what to say -- or what not to say, more importantly -- and not look and blah blah blah blah blah," he said, getting starry-eyed. "But it's like, 'My God, I've actually met the queen!' And it was amazing."
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