Included in the collection are fan letters from Henry Fonda, Charlton Heston, Laurence Olivier and Judy Garland, as well as diaries Hepburn kept while starring in stage productions and notes from producers, playwrights and speech coaches, The New York Times reported Tuesday.
Although some the world's most famous actors praised Hepburn's stage work, the late screen icon's niece, Katharine Houghton, perhaps put it best when she said Hepburn's "relationship with the theater was really very problematic."
Hepburn was fired from her first role, in "The Big Pond" in 1928, after one performance and Dorothy Parker famously skewered her for running "the gamut of emotions from A to B" in the 1933 drama, "The Lake."
"She was basically a very, very shy person, terrified of coming into a room even at family get togethers," Houghton told The Times.
Bob Taylor, the collection's curator, said the public should be able to view the items in February at the Library for the Performing Arts at Lincoln Center.