The Irish Cancer Society (ICS) says it is 'deeply grateful' after it received a €6m donation in a 93-year-old woman's will.
Elizabeth O'Kelly from Stradbally in Co Laois left a total of €30m to five charities after she died in December 2016.
The Irish Independent reports that the Irish Cancer Society, Irish Heart Foundation, Irish Kidney Association, the Irish Society for Autism, and the Royal National Lifeboat Institute Ireland (RNLI) were all left €6m by Mrs O'Kelly.
It is reported she had earned her fortune as a shareholder in a property group, as well as selling her stake in the Leinster Leader newspaper group in 2005.
The ICS says it is the single largest donation they've ever received and is the equivalent of two annual Daffodil Days.
It suggests the funds will help the charity fund 'transformational change' that wouldn't have been possible otherwise.
In a statement, the charity said: "Her generosity will provide hope to so many people affected by cancer and deliver improvements in cancer care that would have been impossible otherwise.
"[She] was known for displaying great kindness towards her friends and being charitable in supporting those in need. This tremendous kindness and generosity is reflected in her decision to leave equal amounts in her will to five charities."
'Enormously generous'
According to the charity, Mrs O'Kelly herself successfully battled cancer in the 1980s - highlighting that survival rates from the disease have doubled since then.
The statement adds: "The Irish Cancer Society won’t give up until Ireland’s cancer services are truly world-class and every patient has the best possible chance of surviving and thriving after a cancer diagnosis.
"We won’t settle for anything less and we know Mrs O’Kelly would not want us to."
The Irish Society for Autism also said it was the largest single donation received by the charity to date.
Deputy executive director Tara Matthews said: “We are greatly appreciative of Mrs O’Kelly’s enormously generous donation. A contribution of this size will have a major impact on the society’s work and help to progress the understanding of autism within Ireland.
"Equipped with knowledge and training, we can all make a significant impact in helping improve the lives of those with autism and their families.”
The society says the money will be used to promote awareness of autism, assist research efforts and train those in contact with people with autism.
'25-times the previous biggest donation'
Meanwhile, Mark Murphy, CEO of the Irish Kidney Association, said the donation was 25-times the group's previous biggest donation.
He explained: "In our wildest dreams we never expected that such generosity would come our way - it represents about four years turnover to us.
"We have a great responsibility now to spend it on behalf of kidney patients throughout the country... It advances the plight of kidney patients tremendously."
He said the charity has bought a house which backs onto the campus of Cork University Hospital, and are working to convert it into a renal support centre.
He also noted they're proposing introducing a haemodialysis facility in Tramore, Co Waterford, beside the association's existing holiday complex.
"Great kindness"
And the RNLI said it was "deeply grateful and humbled" by the generosity of Mrs O'Kelly.
In a statement, the search and rescue charity said: "Mrs O'Kelly... was a long-standing supporter of the RNLI.
"She held a high regard for the volunteer work carried out by the charity which appealed to her ethos and she herself for many years, volunteered her time to help out at an RNLI stall at the RDS in Dublin.
"Throughout her life, she displayed great kindness towards her many friends and was most charitable in supporting those in need.
"This has been reflected in her generous decision to bequest the funds to five charities."
The RNLI added that it will "be carefully considering all options" to ensure the funds are used where they are needed most and "with a view to how they can be spent to fittingly reflect Mrs O'Kelly’s support for the charity."
Additional reporting: Jack Quann