Vicky Phelan, a campaigner who challenged Ireland's cervical cancer screening programme, has died aged 48.
The mother of two, from Limerick, died in the early hours of Monday morning.
The Irish prime minister, Micheal Martin, told RTE Radio she had "extraordinary courage" and was someone "who stood up against the system".
Ms Phelan took legal action after mistakenly getting the all-clear after a smear test in 2011. She was diagnosed with cancer three years later.
Her case prompted others to come forward and raise questions about how women should be involved and informed about their own healthcare, and the issue of open disclosure.
Eventually it emerged that more than 200 women, later diagnosed with cervical cancer, could have been failed by Ireland's screening programme, CervicalCheck.
Dr Gabriel Scally, who led a review into the programme, said she had "a remarkable effect", changing healthcare in Ireland to become "a much more patient, sensitive and respectful system".
Other politicians have spoken about her legacy, with Sinn Fein president Mary Lou McDonald saying Ms Phelan was a "champion of women" who took on the state and won.
Simon Coveney, the Irish foreign minister, posted on Twitter that Ms Phelan's death was "very sad news", adding that she inspired so many people by her "courageous campaigning".
Former Labour leader Alan Kelly told RTE "she was the most incredible human being probably I've ever met" describing her as "resilient" adding she "always fought back".
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Last month a documentary called Vicky was released in Irish cinemas telling Ms Phelan's story.
A digital artwork was projected on to the General Post Office in Dublin to mark its release.
Ms Phelan was awarded the freedom of Limerick this year, and was named as one of the BBC's 100 most inspiring and influential women around the world in 2018.