“Knives Out,” the campy murder mystery now in theaters, is chock-full of A-list stars, including Toni Collette, Daniel Craig, Jamie Lee Curtis and Chris Evans.

So big Hollywood egos must have been crushed when the undisputed star of the film wasn’t an actor with loads of industry awards, but a sweater from your Irish grandpa’s closet.

We’re referring to the distressed Aran knit sweater Chris Evans’ character, Ransom, wears in the movie. And the sight of him in the chunky jumper is sending moviegoers into a frenetic state of social-media swooning.

“I was at the premiere last night and I’m pretty sure people clapped and cheered when that sweater came out,” actress Mara Wilson tweeted.

TV writer Ira Madison III tweeted, “I just ordered Chris Evans’ sweater from Knives Out and I can’t wait to f - - k it.” Meanwhile, even the flick’s official Twitter account has embraced the knitsanity. Its avatar is now a photo of the former Captain America in the jumper, and the name has been changed to “Chris Evans’ Sweater Stan Account.”

The big screen has long created breakout costume moments. Many — like Jennifer Beals’ off-the-shoulder sweatshirt in “Flashdance,” Cher Horowitz’s short plaid skirts in “Clueless” and Marty McFly’s self-lacing Nikes in “Back to the Future Part II” — are either sexy or innovative.

This is neither.

The cream pullover is a traditional sweater the Irish wore to distinguish different family tribes in fishing villages, according to Freda Hayes, the CEO of Blarney Woollen Mills, an iconic knits company based near Cork, Ireland.

Made from wicking wool, the sweater is ideal for the salty seafaring life, but with its star turn in “Knives Out,” it’s shedding ye ol’ utilitarian reputation and embracing its stylish side.

“Everyone in Ireland knows that wearing the traditional Aran is very cool indeed. Especially if it is distressed and worn-looking, in fact that makes it cooler,” Hayes tells The Post.

“The Aran sweater is a lifetime investment, and brings with it lots of luck and a plentiful catch. We have always known that, so maybe only now the world is finding out.”

Blarney Woollen Mills says sales of their Honeycomb Stitch Aran Sweater ($105) have increased 150 percent since the movie was released on Nov. 27. Black Friday accounts for some of the sales, but they attribute about 30 percent of that to the “Knives Out” bump.

Even brands stateside have seen a surge in sweater love: A rep from L.L. Bean tells The Post that sales of their two Irish Fisherman’s sweaters, the Heritage wool sweater and the cotton Signature version, are up 27 percent and 142 percent, respectively, from this time last year.

The movie’s costume designer, Jenny Eagan, points out that the garment’s allure is mostly about the wearer — in this case, matinee idol Evans.

“I’m not sure if it’s the sweater or who’s wearing the sweater,” she told the Hollywood Reporter. “That might be part of it, too. He looks pretty great.”

We enlisted mere male mortals from The Post staff — who don’t have superhero work on their résumés — to test the It sweater’s universal appeal.

Luis Rendon, designer: “It’s so comfortable but it’s actually so fancy, like you wear it at home having coffee, but you could also go out to the theater and be like, ‘I look cute.’ ”

Mike Blinn, senior online sports editor: “The white is a little out of my comfort zone, but I definitely would’ve checked it out in a store. As a person who sweats, it was a little heavy for me, but feels like it would work for a fall weekend sans jacket. I’d probably feel a little self-conscious, but my wife would be all about it — and probably try to steal it.”

Joe Kemp, digital managing editor: “I’ve never felt too comfortable in cable-knit sweaters, but this one wasn’t terrible — it was less stiff and itchy than most that I’ve ever worn. That said, you still wouldn’t ever find me searching for one of these cream-colored gems on a rack anywhere. I’ll gladly let this style stay with Captain America.”

Dante Jean, editorial clerk: “I probably wouldn’t have picked out a white sweater like this for myself if it wasn’t for this story, but now that I’m wearing it, I’m into it. It’s really cozy.”

Juan Arellano, deputy photo editor: “Just showed the pic to my wife and kids — looks like I’m going shopping this weekend. I feel like it’s the type of sweater my wife would buy me and my son would steal. It reminded me of the warmth of coming home after sledding as a kid.”

Noah Manskar, business reporter: “This is definitely the kind of sweater I look for when I’m shopping for myself. It strikes a perfect balance between fitted and roomy that makes you feel both comfortable and confident. I could see myself wearing it lounging around on a Saturday afternoon and then throwing a collared shirt under it for a nice dinner in the evening. I don’t know if everyone can pull it off like Chris Evans, but wearing it definitely made me understand why everyone loves it so much.”

Additional reporting by Catherine Kast and Tayler Bradford