Givenchy set the template for ladylike chic in the 1950s and 1960s, and his restrained style still informs the way Britain's Queen Elizabeth II and older American and Chinese socialites dress.
His 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.
The pair lived in a Renaissance chateau near Paris.
"It is with huge sadness that we inform you that Hubert Taffin de Givenchy has died," it said in a statement to AFP.
It was Givenchy's 40-year friendship with Hepburn, who he met on the set of the 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 for "Funny Face" and "How to Steal a Million" made both of them style icons.
The black sheath dress he made for the opening scenes of the "Breakfast at Tiffany's" was perhaps the most famous "little black dress" of all time -- although fellow Paris fashion legend Coco Chanel is credited with inventing the garment.
It was also the Givenchy look that former US first lady Jacqueline Kennedy adopted for her White House years, sticking to a uniform of shifts dresses, pillbox hats and low-heeled pumps.
The red coat she wore on the campaign trail for the 1960 presidential election was a Givenchy copy.
On a state visit to France the following year, Kennedy made a famously grand entrance in a Givenchy white silk faille dress at a state dinner at the Palace of Versailles, looking as regal as any European monarch's consort.
"Hubert de Givenchy was a symbol of Parisian elegance for more than half a century," his label said Monday.
"He was the first creator to launch a luxury ready-to-wear range. He revolutionised international fashion in creating the timeless looks for Audrey Hepburn, his friend and muse for more than 40 years."
Fashion mogul Bernard Arnault, head of the giant LVMH group which now owns Givenchy, led the tributes, saying that "he was one of the creators who put Paris at the summit of world fashion in the 1950s."
Born in 1927 in Beauvais, France, Givenchy studied at the Ecole des Beaux Arts in Paris.
His first job in the fashion industry was when he worked for Jacques Fath in Paris in 1945. He then worked for Robert Piguet and Lucien Lelong in 1946, and finally for Elsa Schiaparelli (1947-1951).
He opened his own house in 1952. In 1988, Givenchy sold his business to LVMH but remained head of design until his retirement in 1995.
He was loved by the fashion world from his very first collection.
In 1952, the New York Times magazine published an article entitled "A Star Is Born" and l'Album du Figaro also wrote a feature stating that "In one night, Hubert de Givenchy became one of fashion's most famous children with his first collection."