Yves Saint Laurent velvet navy blazer.

Visionary French fashion designer Yves Saint Laurent was the first to launch a ready-to-wear label, YSL Rive Gauche Prêt-à-Porter. The inaugural Rive Gauche boutique — a modern shop in Paris’s bustling, bohemian Left Bank district — offered stylish garments and accessories that were intended to be affordable for a younger generation of fashion enthusiasts. The store featured Mies van der Rohe chairs and played host to actor Catherine Deneuve during its grand opening.

Saint Laurent pioneered “cross-design” in fashion, taking inspiration from street trends to modernize haute couture. He was the first couturier to open boutiques for both men and women. Using traditional menswear fabrics and designs for women, he also literally cross-dressed, giving men and women alike chic pant suits, elegant tuxedo jackets and urban safari gear. By blurring gender-specific design, he empowered individual style while creating a scissor-sharp fashion aesthetic of sensual ease and beauty. Many of his designs are today considered timeless classics. Saint Laurent also consistently used Black models, like Mounia, Iman and Naomi Campbell, and he drew endless inspiration from different ethnicities and cultures, in no small part because of his Algerian roots.

Born to French parents in Oran, Algeria, in 1936, Saint Laurent went to Paris at age 17 to study fashion at the Chambre Syndicale de la Haute Couture. Just two years later, in 1955, his remarkable sketches were shown to Christian Dior, then the world’s reigning couturier, who hired him immediately.

Surprisingly soon thereafter, Dior publicly chose Saint Laurent as his successor, which sadly proved prescient when the fashion legend died unexpectedly, in 1957. A mere slip of a youth, the 21-year-old Saint Laurent was nevertheless up to the challenge. He shook the traditional couture clientele to its core with youthful silhouettes and styles like the A-line trapeze dress that hung with seeming effortlessness from the shoulders, the antithesis of the pinched waists and molded skirts that had been all the rage after the deprivations of World War II.

After a mandated spell in the torturous French military, Saint Laurent suffered a nervous breakdown and was dismissed by Dior in 1962. Out of the ashes rose the Age of Yves. With Pierre Bergé, his then-lover who became his lifelong business partner and friend, the designer founded Yves Saint Laurent YSL to encompass prêt-à-porter, or ready-to-wear. In 1966, they opened the first YSL Rive Gauche women’s boutique in Paris — Rive Gauche is French for “left bank” — followed soon thereafter by YSL Rive Gauche for men. Ready-to-wear materialized during a period of dynamic transformation and experimentation and came to dominate the Paris fashion scene. Saint Laurent had given birth to a global brand.

His revolutionary Mondrian mini dress from 1965 is a core element of his fashion biography. It is a prime example of how Saint Laurent, an avid art lover and collector, looked to painters, from Goya to Picasso, Ingres to Matisse, for inspiration.

With its pure lines and hues, Mondrian’s ground-breaking 1935 color-block painting Composition C transmutes beautifully into a dress that is highly valued by collectors of contemporary fashion and widely copied commercially to this day. The design is the epitome of Saint Laurent’s aesthetic, requiring a meticulous hand piecing of each color block so that, despite the body’s curves, the visual plane is as flat as a canvas when the garment is worn. Mondrian’s purity met its match in Saint Laurent.

“I am no longer concerned with sensation and innovation, but with the perfection of my style,” Saint Laurent said four years before retiring, in 2002. After a long period of ill health, he died at his home in Paris on June 1, 2008.

The vintage YSL Rive Gauche clothing for sale on 1stDibs includes evening dresses and gowns, jackets, shoes, handbags and other items.