It was Saint Laurent's long-time confidante and business partner, Pierre Berge, who announced the news to the world media.
"Gabrielle Chanel gave women freedom. Yves Saint Laurent gave them power," he said on France Info radio. "Like all creators, Yves Saint Laurent had two faces - a public face and private face."
The designer retired from fashion officially in 2002, but his stellar career - which saw him take over haute couture at Christian Dior aged only 21, and give the world some its most iconic looks, such as feted Sixties tuxedo Le Smoking - was shadowed with long-term depression and drug and alcohol problems. He had become increasingly reclusive in his later years.
Christian Lacroix, Jean Paul Gaultier, Marc Jacobs, Oscar de la Renta, Yohji Yamamoto and Vera Wang are just some of the fashion-world names who have publicly paid tribute to the man Diana Vreeland dubbed "the Pied Piper of fashion".
"I think I'm in shock. I'm in fashion today because of him," Wang told WWD. "I lived in Paris right next to his first couture house. My mother adored his work and introduced me to it when I was 16. I feel in love with fashion because of Yves Saint Laurent. He was the first international superstar in the modern era."
Lacroix, too, paid homage to Saint Laurent's legacy.
"Chanel, Schiaparelli, Balenciaga and Dior all did extraordinary things. But they worked within a particular style," he said. "Yves Saint Laurent is like a combination of all of them. He's got the form of Chanel and the opulence of Dior and the wit of Schiaparelli."
Yves Saint Laurent is now spearheaded creatively by Stefano Pilati, who is credited with designing its collections with respect for its founder's aesthetic. Naomi Campbell will be the face of its autumn/winter 2008-9 campaign.
Read Cathy Horyn's reaction on her blog.
Update via NY Mag.com: Details of Yves Saint Laurent's death last night are emerging. WWD reports the designer died of brain cancer.
The legendary couturier passed away in the presence of [business partner Pierre] Berge and longtime friend and muse Betty Catroux. Catherine Deneuve arrived shortly after he died, at 11:10 p.m. Paris time, Berge noted.
Saint Laurent's funeral is scheduled for Thursday at 3:30 p.m. in Paris at the Eglise Saint-Roch at 296 Rue Saint Honoré. French president Nicolas Sarkozy is expected to attend. After the funeral, Saint Laurent's ashes will be sent to his famous Majorelle Garden in Marrakech.