Sitting outside at Gemma, the restaurant at the Bowery Hotel in Lower Manhattan, Jeanne Damas offered a textbook example of what many might call French-girl style.

She was wearing a camel trench coat over jeans, and her brown hair and bangs looked naturally tousled, as if she had woken up that way. Her visible makeup consisted mostly of red lipstick, which had faded into a more natural-looking tint. On cue, a waiter approached to deliver her a black coffee and a croissant.

It was a Wednesday morning in September, and the last day of New York Fashion Week. Ms. Damas, 31, had arrived from Paris the day before.

Later that evening, she would be opening a new store in Manhattan for Rouje, the fashion brand she founded in 2016, which has become known for feminine basics with a Parisian sensibility. Not long after she started the brand, GQ called Ms. Damas “the coolest, most beautiful French girl in France right now.” French Vogue has described her as “the Paris girl personified.”

Rouje, which started as an e-commerce business, has expanded steadily into brick-and-mortar retail. The New York store, on Broome Street in SoHo, is its first in the United States; seven others have opened in Britain and France, including in London, Paris and Bordeaux.

As Rouje has grown, Ms. Damas said, she has made few changes to its aesthetic, which has always been rooted in her own wardrobe. “I never really changed my style since my teenage years: a pair of jeans, an oversized jacket, ankle boots and a wrap dress,” she said.

She first became recognized for her style by blogging about it. (One of her earliest fans was the French fashion designer Simon Porte Jacquemus, who, after connecting with Ms. Damas online, had her model for his brand.) On Tumblr and later on Instagram, she’d post photos of herself on Paris’s cobblestone streets and in outfits that were often accessorized with a glass of red wine or a swipe of red lipstick. Her fondness for red lipstick, she said, inspired her to name her brand Rouje.

Though Rouje has been informed by Ms. Damas’s personal taste, it is hard not to see similarities between her sensibility and that of the singer and actress Jane Birkin, who died in July. Ms. Birkin was British, but for many came to epitomize an effortlessly elegant and particularly French style. With Rouje, Ms. Damas, a native Frenchwoman, has commoditized her version of that style — and has positioned herself and her brand to become new standard-bearers of the French-girl look.

Ms. Damas was recently cast to portray another French-born fashion muse — the jewelry designer Paloma Picasso — in “Kaiser Karl,” a forthcoming Disney+ TV series about the fashion designer Karl Lagerfeld. Jérôme Salle, the director of the series, said Ms. Damas has “a French style but with a modern elegance.” She was a natural fit, he added, to play a woman whom Mr. Salle, 52, described as a former “it girl” in France.

Delphine Courteille, 48, a hairstylist in Paris who has worked with Ms. Damas, said other clients have cited her as an aesthetic inspiration; specifically her hairstyle, which Ms. Courteille described as “very Parisian” and always with “Jane Birkin-style” bangs.

“There’s a lot of femininity and lightness that makes women want to be like her,” Ms. Courteille said of Ms. Damas.

Dhani Mau, 34, the editor in chief of the website Fashionista, said Ms. Damas’s digital presence (she has 1.5 million followers on Instagram) has helped to bring French-girl style, and the references that inspire it, to a wider audience. “Before you had to watch French films, find photographs or go to France,” Ms. Mau said. The fact that Ms. Damas is often seen wearing Rouje clothes on social media, Ms. Mau added, has helped associate the brand with the French-girl look.

Also helpful in advancing that association were photos of the French actress Léa Seydoux wearing a red, printed Rouje wrap dress on the set of the James Bond film “No Time to Die.” “She had our red dress and we didn’t know,” Ms. Damas said, adding that after those photos circulated, she started to see Rouje on “lots of actresses, especially in France.”

In addition to dresses (starting at $220), Rouje sells tank tops ($60), T-shirts ($70) and jeans ($185), the types of easy basics favored by Ms. Birkin. Camille Charrière, an influencer in London who is half French, described such items as a hallmark of French-girl style.

“The French love their basics,” said Ms. Charrière, 36, who is a contributing editor at Elle UK. “The whole point of French style is that it’s something slow that you build over time.”

Isabelle Chaput, 33, a French fashion photographer and content creator who lives in Manhattan, said that the preference for basics stemmed in part from a resistance to keeping up with trends. “Parisians don’t want to look like they are trying too hard,” she said.

Ms. Damas used the word “simplicity” to describe the appeal of French-girl style. “Sometimes,” she said, “it’s boring.”

She said that while Ms. Birkin has had an influence on her and on Rouje, “the style is not about copying.” She described her approach as less about replicating a specific wardrobe than making clothes that evoke a certain lifestyle. “It’s not the dress itself, but the life you have in the dress,” Ms. Damas said.

Her take on the look has been influenced by style outside of France, she added. Some slip dresses she has made for Rouje, she said, were inspired by garments she saw women wearing when she visited New York years ago.

“It’s funny because me and my creative team are not really inspired in France, then we come here and we are inspired by everything,” Ms. Damas said.

“Women in New York are more audacious with their looks which, in my opinion, is liberating,” she said.