It’s ironic yet sincere; glamorous yet tacky; so bad it’s good; too much and just right.

It’s Joan Crawford and Bette Davis playing up their real-life feud on-screen. It’s Lady Gaga and Bradley Cooper playing up their on-screen melodrama on the Oscars stage.

It’s, as Susan Sontag explained, “a woman walking around in a dress made of 3 million feathers.”

It’s camp, and it’s Monday night’s Met Gala theme. And it has the glitterati scratching their heads.

It doesn’t help that the theme — for the party and the accompanying exhibit, opening Thursday — comes from a Sontag essay published in 1964.

Even gala impresario Anna Wintour is nonplussed.

“The only advice I ever really give to [Costume Institute director] Andrew [Bolton] is, whatever the title of the exhibition is, make sure that everybody understands it immediately,” Wintour said in a recent Vogue.com video, adding that the theme “has created a little bit of confusion.”

Camp — not the sleeping-outdoors kind, but the sashay-shantay, over-the-top variety seen in the zany films of John Waters or the fabulous excess of “RuPaul’s Drag Race” — “is an esoteric concept,” historian Monica Sklar, of the Costume Society of America, tells The Post.

“It’s niche. It’s countercultural. It’s the opposite of ‘Heavenly Bodies,’ ” Sklar says, referring to the Costume Institute’s last blockbuster. “And it’s absolutely timely.”

“Camp tends to come to the fore in moments of social and political instability,” the Costume Institute’s Bolton says during Monday’s press preview, citing the 1960s, ‘80s and today as big campy fashion moments. “Camp is by its very nature subversive. It reacts with and against … the status quo.”

Michael Mamp, a fashion professor at Central Michigan University, agrees.

“Camp is about stepping outside of the boundaries of what society typically expects,” he says. “And you see more and more people pushing against those boundaries, especially with gender . . . Dress and fashion is an incredibly powerful tool to explore that.”

Sontag traced camp back to 17th-century France, where Louis XIV built his shrine to artifice and opulence, Versailles.

In that gilded palace, members of the court donned voluminous dresses that completely distorted the human body and towering wigs that defied gravity — a trend that reached its apex with the powdered hair sculptures worn by Marie Antoinette.

Yet no one really called the Versailles aesthetic “camp.” And while the word was used in Victorian England — mostly as coded language for homosexuality, including for the flamboyant writer and aesthete Oscar Wilde — it took a long time for a kind of “camp aesthetic” to coalesce.

Hollywood helped.

“When we look at early films, particularly of the 1930s, we see these celebrations of beauty that is exaggerated and clearly artificial,” says Mamp. He cites the gonzo musicals of Busby Berkeley and the glamorous hauteur of stars like Greta Garbo and Marlene Dietrich, who flaunted convention by appearing in drag without diminishing — and maybe even enhancing — their sex appeal.

Instead of turning off viewers, these improbable, often ridiculous fantasies inspired awe.

“When you look at camp iconography, it’s about individuals who have been willing and who have tried — either through mannerism, or dress, or performance — to step outside of their prescribed box or gender expectation,” says Mamp, adding Joan Crawford, Diana Vreeland, Judy Garland, RuPaul and, more recently, Lady Gaga to the mix.

Campy fashion “uses the artificial to express the authentic,” says Mamp, adding that it leads directly to drag — and today’s increasingly experimental attitudes toward gender and individuality.

It’s why designers nowadays are particularly drawn to camp. It’s pure fantasy, with a wink. It can transform the body (a la Bjork’s infamous swan dress, or Victor & Rolf’s poufy meme ballgowns); blur one’s gender (think “Pose” star Billy Porter’s hybrid tux-dress he wore to the Oscars recently) and revel in what camp hero John Waters calls “good bad taste” (Marc Jacobs’ Joan Crawford-printed dresses, Jeremy Scott’s glitzy odes to Vanna White).

“It is neither nihilistic nor self-defensive,” says Sklar, adding that its embrace of the artificial and fabulous is freeing. “You can say it’s empowering.”

Even Bolton says that the theme is really all about fun.

“The ultimate purpose of camp is to put a smile on our faces,” he says.

Related Video