Richards, who had suffered strokes, died Friday at her home in Burlington, Canada, west of Toronto, said Rick Goldschmidt, who documented the history of "Rudolph the Red-Nosed Reindeer" and its producers.
Like most of the cast, Richards was a veteran of Canadian radio when the producers traveled north to assemble the voices for the program based on the 1949 song "Rudolph the Red-Nosed Reindeer."
Radio dramas were still going strong in Canada in the early 1960s, providing producers with a stable of voice actors, Richards told Filmfax magazine in 2005.
Her trademark — being able to speak like a young boy — was well-established when she took the part of Rudolph, the misfit reindeer who saves Christmas in the stop-motion animation production. She was credited as "Billy Richards," which further obscured her gender.
"Kids won't believe it when my grandchildren tell them that their grandmother is really Rudolph," Richard said in the Filmfax interview, but she said she could prove it by summoning the voice on the spot.
Producers Arthur Rankin and Jules Bass also went to Canada because they could record the voices for the special more cheaply, according to Goldschmidt.
Narrator Burl Ives, who voiced Sam the Snowman, was the show's only celebrity. He also was the only actor to receive long-term residuals, a point that rankled Richards and other Canadians in the production as "Rudolph" became a classic that is still shown during the holidays.
She earned residuals for three years, a business deal she regarded as a "sore subject," Richards said in 2000 in Toronto's National Post.
Yet Rudolph remained her favorite part, Richards once said, and she reprised the role in two sequels, "Rudolph's Shiny New Year" (1976) and "Rudolph and Frosty's Christmas in July" (1979).
Whatever Rudolph did, "he's doing it for a reason," she said in the Filmfax interview. "That's why it's been so popular. That and Burl Ives, for heaven's sake."
Born in 1921 in Toronto, Richards was the daughter of a silverware salesman who had aspired to a stage career.
She was taking dance lessons at age 2, and by 5 she was dancing and singing in stage revues.
During World War II, Richards joined the Canadian Navy and entertained troops in Canada and Europe.
After the war, she studied at the Lorne Greene Academy of Radio Arts in Toronto and went to work at the Canadian Broadcasting Corp.
For 25 years, Richards performed in radio dramas and had her greatest success playing a boy called the Kid on "Jake and the Kid," which aired in the 1950s.
She went on to act in more than 25 film and television projects, including Care Bears movies and animated TV shows.
As it became clear that she would be remembered for giving voice to Rudolph, "she really embraced it," Goldschmidt said.
As Richards said on National Public Radio in 2004: "What better legacy can you leave than a show that everybody loves?"
Richards had four children and 12 grandchildren as of 2005.