Givenchy set the template for ladylike chic in the 1950s and 1960s, dressing everyone from Princess Grace of Monaco to Jane Fonda.
His longtime partner, the former haute couture designer Philippe Venet, announced his death through the Givenchy fashion house, saying he had died in his sleep on Saturday.
"It is with huge sadness that we inform you that Hubert Taffin de Givenchy has died," it said in a statement to AFP.
With his perfect manners and old-school charm, the tall and handsome count was the very acme of French elegance and refinement.
But it was his 40-year friendship with his muse Hepburn, whom he met while she was making Billy Wilder's Oscar-winning comedy "Sabrina" in 1953, that helped make him a fashion legend.
The narrow-collared suits and slim woollen dresses Givenchy designed for the gamine actress in "Funny Face" and "How to Steal a Million" made both of them style icons.