Mr. Donaldson was scheduled to return to the festival this year for his 25th season, playing Buckingham in Richard III and Marcus Andronicus in Titus Andronicus. "Peter was the finest actor's actor," said general director Antoni Cimolino, who worked with Mr. Donaldson on many productions, in a statement. "He was deeply admired for the conviction he brought to his work and the unsparing truth of his portrayals. He was versatile and able to give outstanding performances in modern plays, musicals and classics. But his home was Shakespeare."

Mr. Donaldson was last seen on the Stratford stage in 2008, when he played Rufio in Caesar and Cleopatra, Friar Laurence in Romeo and Juliet, and Don Armado in Love's Labour's Lost.

Peter Donaldson was born and raised in Midland, Ontario, and attended performances at the Stratford Festival as a high school student. A graduate of the University of Guelph, Mr. Donaldson first worked at the Festival in 1977, playing bit parts. He remained for three seasons, and then moved to New York to study with Uta Hagen, Stella Adler and Olympia Dukakis. Thereafter, he performed at a number of Canadian theatres, including the Shaw Festival, Toronto Free Theatre and London's Grand Theatre.

After a single season at Stratford in 1982, Mr. Donaldson returned in 1986, growing into one of the Festival's most versatile leading men. Over 12 seasons, he played Jaques in As You Like It, both Kent and Edgar in productions of King Lear, Guy Thompson in Homeward Bound, Boy Staunton in World of Wonders and Petruchio in The Taming of the Shrew.

In 1994, he played James Tyrone Jr., in Eugene O'Neill's Long Day's Journey Into Night, with William Hutt, Martha Henry, Tom McCamus and Martha Burns. He reprised the role in a film version, winning a Genie for Best Supporting Actor. After that performance, he appeared in Atom Egoyan's film "The Sweet Hereafter." From 1995 to 1999, he worked on the television series "Emily of New Moon."

In 2001, Mr. Donaldson again returned to Stratford to play Malvolio in Twelfth Night, George in Who's Afraid of Virginia Woolf? and Trigorin in The Seagull.

"Peter's work and career reminded me of William Hutt," said Mr. Cimolino. "Like Bill, in his mid-life Peter was now coming into the best, deepest and richest part of his talent."

Sean Arbuckle, a Stratford company member who played Nick to Mr. Donaldson's George in Who's Afraid of Virginia Woolf, told Playbill.com, "Along with the range and integrity of his talent, the people who knew him and worked with him will equally remember his generosity — especially with regards to mentoring younger, newer Festival company members — and his devotion to his beautiful family.

"His was a life that you aspired to emulate not only professionally, but also personally. I worked with him on Virginia Woolf and Timon and Athens and will, of course, especially remember those tremendous performances, but I will also always remember him as Atticus Finch in To Kill a Mockingbird, for which I was merely an audience member. I remember thinking that no one but Pete could've conveyed that sense of honesty and desire for justice and truthfulness, and yet still be the most loving and caring of fathers to [Atticus'] daughter, Scout."

He is survived by his wife, Sheila McCarthy, and daughters Mackenzie and Drew. Details of a funeral and memorial celebration will be announced at a later date.