She played the eldest von Trapp daughter Liesl in the movie.
Charmian Carr died in Los Angeles after complications from a rare form of dementia, her representative said.
The role of Liesl in the 1965 movie includes the famous song Sixteen Going on Seventeen.
After leaving the film industry, Charmian Carr ran an interior design company in California.
Charmian Carr’s mother had arranged for her to audition for the role, although she had had no singing or acting lessons.
The Sound of Music was a massive hit, at the time surpassing Gone with the Wind as the highest-grossing movie of all time.
Charmian Carr later wrote two books on her experience, Forever Liesl and Letters to Liesl.
Kym Karath, who played Gretl in the movie, tweeted: “She has been like a sister throughout my life.”
The real life Liesl, Agathe von Trapp, the eldest daughter of the Austrian family who inspired the movie, died in 2010 at the age of 97.
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