Harris, who was one of Broadway's most honored performers, died of congestive heart failure, according to actress and family friend Francesca James.
"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," said James. The two had known each other for about 50 years.
Harris had suffered two strokes over the years - the first happened in Chicago in 2001, and the other happened in 2010.
During her nearly 60-year career, Harris won a record-setting five Tony Awards for best actress in a play. Her roles ranged from the flamboyant Sally Bowles in "I Am a Camera" to the reclusive Emily Dickinson in "The Belle of Amherst." Her sixth Tony Award was a special lifetime achievement award in 2002.
Harris also appeared on television 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).
Harris was born on Dec. 2, 1925, in Grosse Pointe, Mich. Her father was an investment banker, and she grew up fascinated by movies. She would later study drama in finishing school, prep school, Yale University and the Actor's Studio.
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.
Funeral arrangements are pending.
The Associated Press contributed to this report.