But, actor Fionn Whitehead isn't too pleased with Harry's involvement... well, he isn't pleased with Harry's fans involvement.
Speaking to Digital Spy, he admitted that "He's [Harry] great, he's a good actor and a lovely guy.
"I think the hysteria – [perhaps] it should have been expected when you take a figure like that and give him a short back and sides and put him in a uniform.
"I think it's got a bit silly really. The meaning has got lost somewhere along the way and people have stopped realising there's an amazing cast – including Harry – but there's, you know, the creme de la creme of actors.
"I think the focus should not be Harry Styles doing a movie, it should be on the piece in general or his ability to act. And he's great."
It's true that the film is chocka-block full of amazing actors, like Tom Hardy, Mark Rylance and Cillian Murphy, but c'mon... do they know how much more promo this movie is getting because of Harry??
Dunkirk hits cinemas on July 20, 2017.