Emma Mhic Mhathúna, one of the women at the centre of the cervical cancer controversy, has died in Co Kerry.
Ms Mhic Mhathúna, aged 37, was one of the most public figures in the CervicalCheck crisis.
She was among 221 women with cervical cancer found to have received incorrect results during a clinical audit of past tests by the CervicalCheck screening programme.
The mother of five was given a terminal diagnosis of cancer in May this year and said telling her young family of her diagnosis was the hardest thing she ever had to do.
Ms Mhic Mhathúna received two incorrect smear results.
She said if she had been correctly diagnosed she would have survived.
In June she settled her case against the HSE and the US laboratory, Quest Diagnostics for €7.5 million.
Quest admitted to misreading two cervical smear slides in 2010 and 2013.
The HSE admitted liability for not disclosing the findings of the CervicalCheck audit.
She refused to be viewed as a victim and spoke about her settlement on RTÉ’s Six One News.
Along with others, Ms Mhic Mhathúna campaigned for openness over the CervicalCheck crisis.
She was on some trial treatments but her cancer spread.
Ms Mhic Mhathúna wanted all of her settlement paid into court for the benefit of her five children.
RTÉ News understands that Ms Mhic Mhathúna had been admitted to University Hospital Kerry in recent days and that she passed away there earlier today.
In a statement, her family said she died in the "knowledge that she had helped to shine a light on important issues which affected not just her own life, but the lives of many others".
They added: "Emma's unending and unwavering commitment to her children means that her abiding legacy will be that of a great mother. However, Emma will also be remembered as someone who fought for social justice in an exceptionally selfless way during times of great personal challenge."
Speaking on RTÉ’s This Week programme, Vicky Phelan - who was also diagnosed with terminal cancer after a false negative cervical smear - said: "There are five children left behind here, with the youngest only two."
She added: "It is very upsetting for everybody, but I suppose in my case I am still dealing with terminal illness and it really brings it home... it is very difficult."
"I knew things were bad but you kind of hope that like in my case the immunotherapy drug would take hold and give her a bit more time with the children," she said.
Stephen Teap, whose wife Irene died from cervical cancer after two undisclosed false tests, tweeted: "Another brave momma leaves this world and gets her wings, leaving behind her five lovely children....RIP Emma. Sending love and strength to her children and family."
Additional reporting: Paschal Sheehy, PA