For the last role of her long career, Martha Henry, one of Canada’s finest stage actors, played the character in Edward Albee’s “Three Tall Women” known simply as A. Mr. Albee’s character description reads in part, “a very old woman; thin, autocratic, proud, as together as the ravages of time will allow.”

As Ms. Henry took to the stage at the Stratford Festival in Ontario in August to begin the play’s two-month run, the cancer she had been dealing with for more than a year was well along. She used a walker in the first shows. In September she performed the role from a wheelchair, soldiering on in the demanding part through the final performance, on Oct. 9.

She died of the disease on Oct. 21 at her home in Stratford, the festival announced. She was 83.

The effort Ms. Henry put into her final role — A is a dying woman, mean and prone to bursts of both laughing and crying — was, by all accounts, something to see. The performance “shows the veteran actor at her monstrous best,” J. Kelly Nestruck, the chief theater critic for The Globe and Mail of Toronto, wrote in August.

“It’s unforgettable — which I mean both as praise and as a warning,” he added. “You might not want the woman she plays stuck in your head.”

Ms. Henry had been known for memorable performances at Stratford for decades. She first appeared there in 1962 in a production of “The Tempest,” and her association with the festival continued, with a few gaps, to the present. She acted in more than 70 productions and directed 14 others.

“Her sense of responsibility to the theater was so profound that it enabled her to endure pain and face down her terminal disease to complete an astoundingly truthful performance as a dying woman in ‘Three Tall Women,’” Antoni Cimolino, Stratford’s artistic director, said in a statement. “Her life became art.”

Martha Kathleen Buhs was born on Feb. 17, 1938, in Detroit. Her parents, Lloyd and Kathleen (Hatch) Buhs, divorced when she was 5. Her mother was a pianist who played cocktail lounges and was often working at night, so Martha was raised by her grandparents until she was 14. She was interested in acting at a young age.

“I joined a Brownie troop because they were doing a play,” she told The Pittsburgh Press in 1968.

As a teenager she rejoined her mother, who had become part of a traveling entertainment troupe. She would often go on the road with her, enjoying the company of the other performers.

“On the same bill there’d be a comic — my mother would fill in as the straight woman — a ventriloquist, a snake charmer, a tap dancer,” she told The Edmonton Journal of Alberta in 1996, when she was playing the same role in “Three Tall Women” in an Edmonton production. “I grew up with show people. They were so good to me.”

She enrolled at what is now the Carnegie Mellon University School of Drama in Pittsburgh, choosing it over several other colleges because, as she told The Press, “it was the only one that held auditions, to see what you could really do.”

The drama department did four Shakespeare plays while she was there, she said, but the future star of numerous Shakespeare productions didn’t get into any of them. After graduating in 1959, she did summer stock in Ontario and worked with the Crest Theater in Toronto. Then she enrolled in the National Theater School in Montreal when it was established in 1960, and went on to become its first acting graduate — halfway through the three-year course, as she told The Press, the directors told her that she was ready for a professional career.

Six weeks later she was a member of the Stratford troupe; her debut there was as Miranda in “The Tempest.” One critic called her “the find of the season.”

She had married a fellow student at the theater school, Donnelly Rhodes Henry. The marriage didn’t stick, but the last name did (though not for him — he performed professionally as Donnelly Rhodes). A later marriage, to the actor Douglas Rain in 1968, ended in divorce in 1988. In 1989 she married the actor Rod Beattie, who survives her, along with a daughter from her second marriage, Emma Rain.

At Stratford, Ms. Henry’s Isabella in “Measure for Measure” in 1975, her Beatrice in “Much Ado About Nothing” in 1998 and her Mary in “Long Day’s Journey Into Night” in 1994 were among her most acclaimed performances. She was also artistic director of the Grand Theater in London, Ontario, from 1988 to 1994.

Ms. Henry made the occasional film or television appearance and performed on many stages beyond Stratford, including some in New York. But she said she was never tempted, as a young actress, to try to make it in Manhattan.

“I knew exactly what would happen there,” she told The Journal. “I wasn’t exactly shy, but I wasn’t pushy. I was no great beauty. I could see myself getting an apartment and just staying in it.”

Canada offered what she wanted, she said.

“I just wanted to work, and I felt that any country that could produce a Stratford had to be the most wonderful place. And I was right.”