Daniel Ennis has won the Dublin Central bye-election on the ninth count for the Social Democrats.
Mr Ennis received 3,744 transfers from the Green Party's Janet Horner to finish on 12,050, well ahead of Sinn Féin's Janice Boylan on 7,787.
Ms Horner was excluded after the eighth count, while independent candidate Gerard Hutch was excluded after the seventh count.
Mr Ennis topped the poll after the first count, coming in 555 votes ahead of Ms Boylan in second place. He received 4,903 first preference votes, ahead of Ms Boylan on 4,348 votes.
Ms Horner came in third place after the first count with 2,907 votes, ahead of Mr Hutch, who received 2,817 votes.
Fine Gael candidate Ray McAdam received 2,659 votes, while the other Government party candidate, John Stephens of Fianna Fáil, received 1,049 votes, or 4.2% of first preference votes.
Fianna Fáil lost its deposit after Mr Stephens was excluded from the race after count two.
Watch: Ennis promises to be 'honest, hardworking TD'
He was excluded with a total of 1,120 votes - below the threshold to save the deposit.
Speaking in Salthill, where the Galway West vote count is taking place, Taoiseach Micheál Martin said his party will reflect on the results of the bye-elections.
Asked about his party's low first preference share in Dublin Central, Mr Martin said there were "historic problems" in the constituency.
Watch: Final count announcement in Dublin Central
Pointing out that the party last won a Dáil seat there in 2007, he said: "We have a weakness there… so we have a lot of work to do there and we know that."
"I’ve been through bye-elections where we did poorly... modern politics is very fragmented and in some instances it will take two to three electoral cycles to get elected," he said.
Sinn Féin leader Mary Lou McDonald looked forward to the party's performance in the next general election as a barometer when asked if she was concerned by her party's drop in votes in Dublin Central since 2020.
"I would humbly suggest to you that when a general election comes, when a general election lands, watch and see how we perform," she said.
Ms McDonald added she is "absolutely determined" that at the next general election "we'll see the back of Fianna Fáil-Fine Gael government".
The Sinn Féin leader said her party is "building".
She said Sinn Féin will "go at it again and we'll build again, and more successfully again" in Dublin Central.
The Social Democrats increased its share of first preference votes in Dublin Central by 6.4% from the last general election, with the Green Party also seeing an increase of 5.7%.
Sinn Féin was down 5.9% on its general election performance in the constituency when Ms McDonald was elected.
Earlier, Social Democrats TD for the constituency Garry Gannon said that the party is "obviously delighted" with the tally.
"It is a real endorsement of the type of politics Social Democrats stand for and Daniel too," he said.
The turnout stood at 43.5%, compared with 52.3% in the 2024 General Election.
The bye-election was caused by Fine Gael's Paschal Donohoe leaving politics for a senior role in World Bank in the US.
