Audrey Hepburn, the actress who epitomized Hollywood chic in the 1950's and 60's, died yesterday at her home in Tolochenaz, near Lausanne, Switzerland. She was 63 years old and had undergone surgery for colon cancer in November.

Her death from cancer was announced by Unicef, the United Nations Children's Fund, for which she had been a special ambassador since 1988.

In recent years, she made few movies, but traveled the world raising money and awareness for the U.N. organization. Her last screen role, in 1989, was a cameo as an angel easing the hero toward death in Steven Spielberg's "Always," a role in which the character's grace and serenity echoed the image Miss Hepburn had maintained throughout a 40-year career. An Oscar for a Princess

Her first major film role made her a star. In the 1953 romance "Roman Holiday," she played a princess who runs from her duties and falls in love with a journalist played by Gregory Peck. Audiences were enchanted by her combination of grace, elegance and high spirits, and she won an Academy Award as best actress.

The same year she won her Oscar, she won a Tony for her performance in the play "Ondine." Bosley Crowther, The New York Times critic, described her in words that characterized her youthful appeal. He called her "a slender, elfin and wistful beauty, alternately regal and childlike."

In a string of films that followed, she continued to play the lithe young thing with stars in her eyes and the ability to make Cinderella transformations. In "Sabrina" (1954), she was a chauffeur's daughter forced to choose between wealthy brothers, played by William Holden and Humphrey Bogart. In "Funny Face" (1957), opposite Fred Astaire, she played a bookstore clerk turned high-fashion model.

Descriptions of her beauty and appeal inevitably included the word "gamine." She was boyishly slender, with an aristocratic bearing, the trace of a European accent and a hint of mischief. 'A Wild-Eyed Doe'

Billy Wilder once recalled directing her in the 1957 film "Love in the Afternoon": "You looked around and suddenly there was this dazzling creature looking like a wild-eyed doe prancing in the forest. Everybody on the set was in love within five minutes."

Among her most popular and acclaimed roles was that of Holly Golightly, the backwoods beauty turned New York sophisticate in "Breakfast at Tiffany's" (1961).

At the height of her career, she worked with such directors as William Wyler and George Cukor and acted with the great male movie stars of her day, playing the younger woman opposite Gary Cooper ("Love in the Afternoon"), Cary Grant ("Charade," 1963) and Rex Harrison, in the 1964 movie version of "My Fair Lady."

There was some grumbling from the theater world when she was cast as Eliza Doolittle in "My Fair Lady," winning the role over Julie Andrews, who had originated it on Broadway. Ms. Hepburn's singing was dubbed in the film by Marni Nixon. The film won several Oscar nominations, but Miss Hepburn was not nominated. A Blind Woman Terrorized

Throughout her career, she also took on dramatic roles. She won an Oscar nomination for the title role of a woman questioning her vocation in "A Nun's Story' (1959). She played a woman enduring 20 years of an embattled marriage, opposite Albert Finney, in "Two for the Road" (1967). And she won her fifth Oscar nomination for her role as a blind woman terrorized in her own home in "Wait Until Dark" (1967). Other nominations were for "Sabrina" and "Breakfast at Tiffany's."

After "Wait Until Dark," she left full-time acting and lived mostly in Switzerland.

Miss Hepburn returned to the screen occasionally. In "Robin and Marian" (1976) she played the middle-aged Maid Marian to Sean Connery's Robin Hood. The role was considered the triumph of her later career and a reflection of the graceful way the actress herself had moved into middle age.

She also made some poorly received films, including "Bloodline" (1979) amd "They All Laughed" (1981).

Miss Hepburn, whose name originally was Edda van Heemstra Hepburn-Ruston, was born on May 4, 1929, near Brussels, to a Dutch mother and an English father, and was educated largely in London. During World War II, she and her mother were caught vacationing in Holland when the Nazis invaded and her family endured much hardship during the occupation. During the war, one of her brothers was taken to a labor camp, and an uncle and cousin were executed. She once said the family was reduced to eating tulip bulbs. Spotted by Colette

But when she returned to London after the war, her life took the glamorous turn she would maintain for the rest of her life. She was a ballet student and model. On the Riviera, she was spotted by the author Colette, who insisted that Miss Hepburn star in the Broadway version of "Gigi," which led to "Roman Holiday."

She attributed her work with Unicef to her childhood experience of hunger and fear during the war.

As Goodwill ambassador for Unicef she traveled extensively in Africa and Latin America. She visited Ethiopia during the drought to call attention to the plight of starving children. In 1991 she described her Unicef role as "talking my head off," and said, "I just decided to do as much as possible in the time that I'm still up to it."

Last year she visited Somalia. It was shortly after returning from that trip that her cancer was diagnosed. With Frequent Appearances

Even in her last years she remained a visible presence in the film world. She received a tribute from the Film Society of Lincoln Center in 1991. She was a frequent presenter at the Academy Awards, and the Academy of Motion Picture Arts and Sciences recently announced that she and Elizabeth Taylor would receive the Jean Hersholt Humanitarian Award this year.

In 1954, she married the actor Mel Ferrer (with whom she later co-starred in "War and Peace.") They were divorced in 1968. In 1969 she married Andrea Dotti, an Italian psychiatrist, from whom she was later divorced.

Her companion since 1980 was Robert Wolders, a Dutch actor. She is also survived by two sons, Sean, from her marriage to Mr. Ferrer, and Luca, from her marriage to Dr. Dotti. The Sprite in Designer Clothing