Maria Steen has fallen short of the 20 required signatures to enter the presidential race, as the nomination window closed with just three candidates confirmed.
To be eligible to run, a candidate must be over the age of 35 and have been nominated either by 20 members of the Oireachtas or four local authorities.
No candidate was successful through the local authority route after most councils decided not to nominate any candidate, with the majority of councillors from the largest parties choosing to oppose independent hopefuls.
Ms Steen, who was a prominent voice among those campaigning for “no” votes in referendums on abortion and same-sex marriage, had received the backing of 18 TDs and senators to get on the ballot paper – but this was insufficient.
She also campaigned on the “no” side in last year’s referendums on family and care, which were defeated.
Conceding the end of her bid, Ms Steen told reporters outside Leinster House on Wednesday that she was “humbled by the outpouring of support” for her campaign.
She added: “While I’m honoured to have received 90% of the required signatures from members of the Oireachtas, I regret to say it was not enough and that time has now run out.”
Ms Steen said the public’s “hunger for an alternative candidate” will now go “unsatisfied”.
She added: “My effort to make that the ballot has not been successful, but I do not feel like I have lost – I have the privilege of returning to life at home with a wonderful family.”
It leaves just three candidates in the race, ahead of voting day on October 24.
Fianna Fail candidate Jim Gavin and Fine Gael candidate Heather Humphreys filed their nomination papers last Friday.
Independent candidate Catherine Connolly, who is supported by left-wing parties Sinn Fein, the Social Democrats, Labour, People Before Profit and the Greens, submitted the documentation on Tuesday.
Mr Gavin, a married father-of-two, is most prominently known for his role as manager of the record-breaking Dublin side which won five successive All-Ireland Championships.
While not a career politician, he was put forward as the preferred candidate by party leader and Taoiseach Micheal Martin.
Mr Gavin’s career within Ireland’s Defence Forces has been cited by Mr Martin as an example of why he would make an “outstanding” president.
His 20-year career saw him take on many roles as a commissioned officer and military pilot, also holding posts such as chief flying officer.
Mr Gavin was appointed the chief of military aviation for the United Nations peacekeeping mission operating in the Central African Republic and Chad in 2010.
Ms Humphreys had initially ruled out seeking a presidential bid and backed Fine Gael’s first candidate Mairead McGuinness.
However, after Ms McGuinness withdrew on health grounds, she emerged as the party’s new hopeful.
Ms Humphreys was a TD for Cavan-Monaghan between 2011 and 2024 before announcing she would not contest the next general election.
She previously served as deputy leader of Fine Gael and Minister for Social Protection.
Ms Connolly worked as a barrister and a clinical psychologist before becoming a councillor for 17 years and spending a term as Galway mayor until 2005.
She resigned from the Labour Party in 2006 after being turned down to be a running mate of then incumbent TD Michael D Higgins.
She was first elected to the Dail as an independent candidate for Galway West in 2016 and later became Leas-Cheann Comhairle.
The race also saw other candidates launch bids of varying degrees of seriousness and success.
Pharma tycoon Gareth Sheridan, aged 36, received the backing of two county councils but failed to convince enough local representatives to nominate him.
Mr Sheridan said on Wednesday that the nomination process for the presidency is no longer fit for purpose.
Fianna Fail saw internal disquiet as both MEP Billy Kelleher and former leader Bertie Ahern unsuccessfully sought the party’s nomination.
Elsewhere, mixed martial arts fighter Conor McGregor, Riverdance star Michael Flatley and weather forecaster Joanna Donnelly were among well-known names to have sought a nomination.
