Harris died at her West Chatham, Mass., home of congestive heart failure, actress and family friend Francesca James said.
The actress won five Tony Awards for best actress in a play, displaying a virtuosity that enabled her to portray an astonishing gallery of women during a theater career that spanned almost 60 years and included such plays as The Member of the Wedding (1950), The Lark (1955), Forty Carats (1968) and The Last of Mrs. Lincoln (1972).
She was honored again with a sixth Tony, a special lifetime achievement award in 2002.
Harris had suffered a stroke in 2001 while she was in Chicago appearing in a production of Claudia Allen's Fossils. She suffered another stroke in 2010, James said.
"I'm still in sort of a place of shock," said James, who appeared in daytime soap operas All My Children and One Life to Live. "She was, really, the greatest influence in my life."
Television viewers knew Harris as the free-spirited Lilimae Clements on the prime-time soap opera Knots Landing. In the movies, she was James Dean's romantic co-star in East of Eden (1955), and had rolls in such films as Requiem for a Heavyweight (1962), The Haunting (1963) and Reflections in a Golden Eye (1967).
Yet Harris's biggest successes and most satisfying moments have been on stage. "The theater has been my church," the actress once said. "I don't hesitate to say that I found God in the theater."
The 5-foot-4 Harris, blue-eyed with delicate features and reddish-gold hair, made her Broadway debut in 1945 in a short-lived play called It's a Gift. Five years later, at the age of 24, Harris was cast as Frankie, a lonely 12-year-old tomboy on the brink of adolescence, in The Member of the Wedding, Carson McCullers' stage version of her wistful novel. The critics raved about Harris, with Brooks Atkinson in the New York Times calling her performance "extraordinary – vibrant, full of anguish and elation."
"That play was really the beginning of everything big for me," Harris had said. The actress appeared in the 1952 film version, too, with her original Broadway co-stars, Ethel Waters and Brandon De Wilde, and received an Academy Award nomination.
In 2005, she was one of five performers to receive Kennedy Center honors.
Harris was born on Dec. 2, 1925, in Grosse Pointe, Mich., the daughter of an investment banker. She grew up fascinated by movies, later saying she thought of herself as plain-looking and turned to acting as a way of becoming other persons. She made her stage debut at the Grosse Pointe Country Day School in The Hunchback of Notre Dame at age 14. In the years that followed, she studied drama in finishing school, prep school, Yale University and the Actor's Studio.
Before Knots Landing, Harris made numerous guest-starring television appearances on dramas and was a regular on two quickly canceled series – Thicker Than Water in 1973 and The Family Holvak in 1975. Her Emmys were for performances in two Hallmark Hall of Fame presentations: Little Moon of Alban in 1958 and Victoria Regina in 1961.
Harris was married three times, to lawyer Jay I. Julian, stage manager Manning Gurian and writer William Erwin Carroll. She had one son, Peter Alston Gurian.