"I knew I was in the running, yes, but I never thought I would win," the 82-year-old said by telephone when contacted by The Canadian Press in Victoria, British Columbia.
Munro is beloved among her peers, from Lorrie Moore and George Saunders to Margaret Atwood and Jonathan Franzen. She is equally admired by critics. She won a National Book Critics Circle prize for "Hateship, Friendship, Courtship, Loveship, Marriage," and is a three-time winner of the Governor General's prize, Canada's highest literary honor.
Atwood a fellow Canadian who also figured prominently in the Nobel buzz tweeted, "Hooray! Alice Munro wins 2013 Nobel Prize in Literature."
Munro's publisher, Penguin Random House, welcomed the award with "jubilation and great pride," and sent "joyous good wishes to our beloved author and to our family of her publishers and editors." Canadian Prime Minister Stephen Harper congratulated Munro on Twitter "on behalf of all Canadians."
The award is likely to be the capstone to Munro's career. She told Canada's National Post in June that she was "probably not going to write anymore."
In announcing the Nobel Prize, the Swedish Academy called her a "master of the contemporary short story." The academy's permanent secretary, Peter Englund, said he had not managed to get hold of her but left a message on her answering machine.
"She has taken an art form, the short story, which has tended to come a little bit in the shadow behind the novel, and she has cultivated it almost to perfection," Englund told The Associated Press
Munro is the 13th female literature laureate in the 112-year history of the Nobel Prizes.
Her published work often turns on the difference between Munro's youth in Wingham, a conservative Canadian town west of Toronto, and her life after the social revolution of the 1960s.
In an interview with AP in 2003, she described the '60s as "wonderful."
It was "because, having been born in 1931, I was a little old, but not too old, and women like me after a couple of years were wearing miniskirts and prancing around," she said.
Some have called her "the greatest author in North America and, yes, I tend to agree with that," said the academy's Englund. "We're not saying just that she can say a lot in just 20 pages more than an average novel writer can but also that she can cover ground. She can have a single short story that covers decades and it works."