The death has occurred of Florence Noonan, the wife of Finance Minister Michael Noonan. She was 68.
A native of Castlemaine in Co Kerry, Mrs Noonan, known as Flor, was married to Mr Noonan for 43 years.
They had five children - three sons Tim, John and Michael, and two daughters Orla and Deirdre. Mrs Noonan was a teacher by profession.
Mr Noonan spoke on RTÉ's The Frontline programme in May 2010 about his wife's battle with Alzheimer's Disease and how he and his family had to take the very difficult decision to place her in long-term nursing care.
Mrs Noonan became ill with pneumonia two weeks ago and had to be moved to acute care at the Mid Western Regional hospital.
She died late last night at Milford Hospice in Co Limerick.
Taoiseach Enda Kenny said: "On behalf of the Government, I express my deep condolences to Minister for Finance Michael Noonan on the passing of his wife Florence.
"Our thoughts and prayers are with Michael, their daughters and sons, and their extended family at this time of great loss."
Fine Gael Chairman Charlie Flanagan said: "Our thoughts, our prayers and our support are with Michael and his children on the loss of a wonderful wife and mother and a fine person."
Fianna Fáil leader Micheál Martin said he was "deeply saddened" to hear about Mrs Noonan's death.
He said: "I want to extend my condolences, those of my party and the whole Fianna Fáil organisation to Michael and his children."
Tánaiste Eamon Gilmore has expressed his deepest sympathies with Mr Noonan.
Mr Gilmore said his thoughts were with Minister Noonan and his family at this "very difficult time".
Sinn Féin leader Gerry Adams expressed his condolence and said his thoughts and sympathies are with Mr Noonan.
"I also extend my condolences to their children at their great loss," he added.
There will be requiem mass for Florence Noonan on Sunday in Dooradoyle in Limerick, followed by her burial in the village of Loughill.