Funicello died peacefully at Mercy Southwest Hospital in Bakersfield, Calif., of complications from multiple sclerosis, according to Disney.
Disney first made the announcement via its official fan club's Twitter feed. The post on Disney's D23 Twitter feed reads:
"We're sorry to report beloved Disney Mouseketeer and iconic teen star Annette Funicello has passed away at age 70"
Funicello was a Mouseketeer on "The Mickey Mouse Club" in the 1950s. She was just 13 when she gained fame on Walt Disney's television kiddie "club."
Funicello soon began receiving 8,000 fan letters a month, 10 times more than any of the 23 other young performers.
She also starred in movies such as "Babes in Toyland" in 1961 and the beach party film "How to Stuff a Wild Bikini" in 1965. She also became a recording star, singing on 15 albums and hit singles such as "Tall Paul" and "Pineapple Princess."
"She will forever hold a place in our hearts as one of Walt Disney's brightest stars, delighting an entire generation of baby boomers with her jubilant personality and endless talent," said Bob Iger, Disney chairman and CEO.
Funicello stunned fans and friends in 1992 with the announcement she was suffering from MS. Yet she was cheerful and upbeat, grappling with the disease with a courage that contrasted with her lightweight teen image of old.
When it was finally diagnosed, she later recalled, "I knew nothing about (MS), and you are always afraid of the unknown. I plowed into books."
Her symptoms were relatively mild at first, but gradually she lost control of her legs, and she feared people might think she was drunk. So she went public with her ordeal in 1992.
She wrote of her triumphs and struggles in her 1994 autobiography, "A Dream Is a Wish Your Heart Makes" - the title taken from a Disney song. In 1995, she appeared briefly in a television docudrama based on her book. And she spoke openly about the degenerative effects of MS.
"My equilibrium is no more; it's just progressively getting worse," she said. "But I thank God I just didn't wake up one morning and not be able to walk. You learn to live with it. You learn to live with anything, you really do."
"I've always been religious. This just makes me appreciate the Lord even more because things could always be worse. I know he will see me through this."
Funicello was born Oct. 22, 1942, in Utica, N.Y., and her family moved to Los Angeles when she was 4. She began taking dance lessons the following year and won a beauty contest at 9. Then came the discovery by Disney in 1955.
"I have been blessed to have a mentor like Walt Disney," she said 40 years later. "Those years were the happiest of my life. I felt that back then. I feel the same today."
In 1965, Funicello married her agent, Jack Gilardi, and they had three children, Gina, Jack and Jason. The couple divorced 18 years later, and in 1986 she married Glen Holt, a harness racehorse trainer.
Former Mouseketeers who appeared on later seasons of "The Mickey Mouse Club" include singers Britney Spears, Christina Aguilera, JC Chasez and Justin Timberlake and actors Ryan Gosling and Keri Russell.
Disney is the parent company of ABC7.
The Associated Press contributed to this report.