“Serge was a great man. I was just pretty,” Jane Birkin was wont to say. But in the fashion industry, where Birkin’s impact as a style icon is unmistakable, few are likely to agree with that disparaging self-assessment.

Long before stars relied heavily on stylists and creative directors to shape their image, the British French actress and singer — who died Sunday at the age of 76 — used her unique sense of dress to project a new kind of femininity laced with nonchalance and sexual liberation. Her gamine figure and effortless styling became essential references in France and beyond, influencing fashion far beyond the Hermès bag that famously bears her name.

Today, Birkin continues to inform designers like Celine creative director Hedi Slimane, fashion editor Emmanuelle Alt and scores of contemporary brands from A.P.C. to Sézane, have built global businesses around the French-girl-chic template she shaped.”

In a written comment, Slimane said he had “long been touched by her grace, her depth, her intelligence, her voice.” After meeting Birkin in the early 2000s, he designed suits for her during his tenures at Dior Homme, Saint Laurent and now Celine, and photographed the star in 2016. “She is an eternal icon; eternal youth and beauty, " he added.

Birkin, who rose to stardom in the late 1960s alongside French musician Serge Gainsbourg (her partner until 1980), projected a more innocent, sensual alternative to the ultra-polished cinematic glamour of contemporaries like Catherine Deneuve, and a more coquettish take on sexuality than the beachside bombshell persona of Brigitte Bardot.

While Birkin’s early steps in fashion were as a muse of Paco Rabanne — whose minidresses never made more sense than when exposing her thighs — the star mostly styled herself, applying an unassuming, spontaneous touch that elevated simple pieces like white button-ups, jeans and knit dresses. In the 1970s, Birkin came to embody free-spirited “boho” chic — carrying market baskets as handbags was her idea — but avoided getting weighed down in the ruffles and prints that time-stamp many looks from the period.

Later, when she took to the stage as a singer in the 1980s and 1990s, Birkin worked to refocus the narrative from her baby-doll beauty to her art, shearing off her signature bangs and dressing in androgynous garb that remains the mainstay of many female rockers today: an international sex symbol, now in green army jackets, mens blazers, schlumpy knitwear and jeans, Birkin used fashion to propel herself into a new phase of life and in the public eye.

Put-together but relaxed, everyday yet elevated, Birkin resisted being put in a box. Careful not to be cast as overly precious by her association with luxury house Hermès (whose CEO designed the $10,400 bag bearing her name to meet her needs as a young mother), Birkin would toss the bag around like it was nothing until she stopped wearing it due to tendonitis, and decorated it with stickers for humanitarian causes like Medecins Sans Frontieres.

The notion of “la Parisienne” was indelibly changed by Birkin’s touch: while her fame was most pronounced in France and England, the idea of “French girl” style as synonymous with understated, easy-going elegance continues to grip fashion’s imagination. An echo of Birkin’s influence could be felt at Valentino’s most recent haute couture outing at the Château de Chantilly, where Kaia Gerber opened the show with a white button-up shirt tucked loosely into a pair of trompe l’oeil gazar dungarees.

While the notion of “personal branding” didn’t become widespread until decades after Birkin’s rise, she was surely a master of it: not only could she embody variations of the gamine, the Parisienne and the rocker chick to perfection, she also played a key role crafting the public image of Gainsbourg, who adopted the crumpled shirts and three-day beard that became his signatures at her advisement.

Birkin’s own style—which ranged from provocative outings like dark panties under transparent mini-dresses to an embrace of ultra-androgynous, utilitarian garb — told the story of a woman who spent decades juggling her roles as an artist, as an icon of 20th century sexual liberation, and as a devoted partner and mother.

Her three daughters followed in her footsteps: Charlotte Gainsbourg and Lou Douillon also have made careers leveraging their unique personal styles in cinema and music, while Kate Barry (who died in a tragic fall in 2013) was a fashion photographer working for British Vogue and Paris Match.

Editors’ Note: This story has been modified 17th July 2023 at 15:40 BST. Updates to include comment and photograph by Hedi Slimane.