The great Gucci reset is here. On Wednesday, the Italian fashion house named Demna, the mononymic designer who transformed Balenciaga from a niche luxury house into one of the most provocative, boundary-breaking brands of the last decade, as its new artistic director. He will be in charge of women’s wear, men’s wear and accessories.

Gucci and Balenciaga are owned by Kering, the French conglomerate that also owns Saint Laurent, McQueen, Brioni and Bottega Veneta. A new designer for Balenciaga has not been announced.

“Gucci stands for fashion authority,” Stefano Cantino, the chief executive of Gucci, said. “This is what we want to bring back.”

Demna will be the first “star” designer with a proven track record in Gucci’s 104-year history, a seeming acknowledgment of the crisis it has experienced over the last two years after an apparent attempt to recast itself as a timeless luxury brand. Revenue plunged 23 percent in 2024, and the Kering stock price has more than halved since 2023. (Gucci is by far the largest brand in the Kering stable.)

The appointment will add yet more turmoil to an already unsettled fashion world in which a record number of fashion companies have changed design heads in the last year. Half of Kering’s brands alone will have new designers in 2025.

“We were looking for a strong and opinionated designer,” Mr. Cantino said. “Demna is one of the few.” He brings with him not just design skills, Mr. Cantino said, but “an understanding of contemporary culture, of what is luxury today and a deep understanding of the new generation.”

He also brings a certain knowledge of Gucci. In 2021, Demna and Alessandro Michele, the Gucci designer at the time, “hacked” into each other’s brands to reinterpret their most recognizable designs, with Demna replacing Gucci’s famous double Gs with Bs on its classic logo canvas accessories. And he has the confidence of the Kering chief executive François-Henri Pinault, who once told The New York Times he believed Demna could create a “megabrand.”

When Mr. Pinault named the Georgian-born Demna Gvasalia (he dropped his surname in 2021) to Balenciaga in 2015, however, the fashion world was shocked.

Though Demna, now 43, had received his master’s degree from the Royal Academy of Fine Arts in Antwerp, Belgium, and trained in the studios of Martin Margiela and Louis Vuitton, he made his name at Vetements, a cultlike label created in 2014 that became a fashion sensation almost overnight because of its nose-thumbingly antifashion aesthetic. (Demna left Vetements in 2019.)

Nonetheless, during Demna’s 10 years at Balenciaga, revenues grew close to $2 billion from an estimated $390 million, challenging the meaning of luxury, value and authenticity in the process.

He took the quotidian — Crocs, IKEA totes, even garbage bags — and put them on a pedestal. He almost single-handedly started the monster sneaker trend. He put all ages and genders and kinds of beauty on his runway and created shows that were immersive, apocalyptic experiences that acted as forms of social criticism as much as fashion: shows about the climate crisis, the war in Ukraine, celebrity and the rule of capitalism. He scandalized and thrilled in equal measure.

He collaborated with “The Simpsons,” made Balenciaga video games and attended the Met with Kim Kardashian. He also restarted the couture line and never lost sight of the purity of silhouette that characterized the work of Balenciaga’s namesake designer, Cristóbal Balenciaga.

Balenciaga’s momentum came to an abrupt halt in 2023, when a misjudged holiday ad campaign precipitated online allegations of pedophilia, and Demna’s deep friendship with Ye cast a shadow on the brand in the wake of Ye’s antisemitic rants. Cancellation loomed, but Balenciaga eventually distanced itself from the controversy, and it has since recovered some of its strength. In January, Demna was made a Chevalier des Arts et des Lettres in recognition of his contribution to French fashion. He wore a T-shirt.

Demna’s last Balenciaga show, held on March 9 in Paris, was a career retrospective of sorts and a reminder of just what he had brought to the house. After the show, he joked to reporters that the reason he was wearing a suit for the first time was that he was Demna 2.0.

The Gucci news suggests it was less a joke than it seemed at the time.

“Demna’s contribution to the industry, to Balenciaga and to the group’s success has been tremendous,” said François-Henri Pinault in a news release. “His creative power is exactly what Gucci needs.”

Francesca Bellettini, the deputy chief executive of Kering, called him “the perfect catalyst.”

Demna replaces Sabato De Sarno, a designer who had worked behind the scenes at Valentino before being charged with Gucci’s reset after the seven years of Alessandro Michele’s magpie maximalism. (Mr. Michele had likewise been a number two before ascending to his position, working for the former Gucci designer Frida Giannini.) Though the Michele era had buoyed Gucci to annual revenues of about 10 billion euros, tastes began to swing away from his trademark eccentricity, and Gucci management thought a return to discretion was the answer.

That turned out to be wrong. Instead of positioning the brand as a somewhat more hip equivalent of Hermès, Mr. De Sarno’s luxury minimalism simply made it seem diminished. (It turns out one Hermès is enough.) Demna’s job will be to change all that, though he will have to overcome not just the problems of Gucci, but also the challenge of a slowdown in the broader luxury industry.

In that lies a certain appeal, Mr. Cantino said.

For Demna, Mr. Cantino said, the idea of “being able to make a success at Gucci, prove he is capable of doing something different than Balenciaga and show a different point of view, was very exciting.”

Gucci did not confirm when Demna would show his first collection, but he will begin in early July after his final Balenciaga couture show. (Gucci is not a couture house.) He will split his time between his home in Switzerland and the Gucci headquarters in Milan.