Tributes have been flooding in for the opera singer who has been described as having the 'most secure and compelling soprano voice that Ireland has ever produced'.
Ms O'Sullivan studied at the Cork School of Music and was one of the best known Irish singers of her generation.
She won the Young Musician of the Future award in 1990 and went on to have a successful career both in Ireland and internationally.
She achieved her first major role in 1996, at the age of 34, as Donna Anna in Don Giovanni with Welsh National Opera.
In 1997 and 1998, the Cork woman starred as the Queen of the Night in the Opera North performances of The Magic Flute.
Taoiseach Micheál Martin said he was "deeply saddened to hear of the death of soprano Cara O’Sullivan. She had a beautiful voice and the warmest personality.
"Cork is very proud of her legacy and I will always value our friendship. Deepest sympathy to Christine and her wider family. R.I.P. Cara."