Taoiseach Simon Harris has apologised on behalf of the State to the families of the victims who died in the Stardust fire tragedy.
In 1981, 48 people were killed when the blaze ripped through the nightclub in Artane.
"I know there have been many times when you thought this day would never come," Mr Harris said.
"I know you were forced to endure a living nightmare which began when your loved ones were snatched from you in a devastating fire," he said.
After a more than 40-year campaign for justice, last week an inquest found that the 48 victims had been unlawfully killed.
Mr Harris said the State failed the families of the Stardust victims when "you needed us the most".
Politicians and others gathered in the Dáil welcomed and gave a standing ovation to the Stardust families who gathered in the public gallery.
"Their unfinished stories became your story. The defining story of your lives and the lives of your parents and other family members who left this life before ever seeing justice," Mr Harris said
He added: "I am deeply sorry you were made to fight for so long that they went to their graves never knowing the truth.
"Today we say formally and without any equivocation, we are sorry.
"We failed you when you needed us the most, from the very beginning we should have stood with you but instead we forced you to stand against us."
Family members gathered in the distinguished visitors' gallery and public gallery in the Dail chamber to listen to the Taoiseach.
Mr Harris said he hopes the apology and statements in the Dáil help the Stardust families heal.
"I truly hope that the days since last Thursday have marked a turning point and here today in Dáil Éireann we finally begin to put things right," he said.
"To bring you in from the cold and end the neglect of 43 years waiting and fighting for the only thing you ever wanted, the truth. Nothing else. No other agenda, just the truth."
A previous finding in 1982 said the fire had been started deliberately, a theory the families never accepted.
That ruling was dismissed in 2009, leading to the latest inquests for the victims, who were aged from 16 to 27 and mostly came from the surrounding north Dublin area.
Last Thursday, the jury in the inquests returned a verdict that all 48 victims were unlawfully killed.
A majority decision from the seven women and five men found that the blaze, which broke out in the early hours of Valentine's Day 1981, was caused by an electrical fault in the hot press of the bar.
The Taoiseach read out the names of each of the 48 victims to the Irish parliament, along with a few words about their personalities and hobbies and dreams.
He added: "We think as well of the hundreds of people who were injured and who are scarred forever, physically and mentally scarred by fire and scarred by survival.
"We think of the people working in the Stardust, the waiters, the waitresses, the doorman, the DJs.
"We think of the frontline workers who fought to save lives on the night. The fire crews, the ambulance and hospital staff, and the taxi drivers.
Mr Harris said: "As Taoiseach on behalf of this State, I apologise unreservedly to all the families of the Stardust victims and all the survivors for the hurt that was done to them and for the profoundly painful years of struggle for the truth."
He apologised "to the families that those present on the night of the fire were wrongly criminalised through the allegation of arson, which was an attack on their reputations".
"Every person there was innocent," Mr Harris added.
Sinn Féin leader Mary Lou McDonald said that the families were met with "callousness" which set the tone for 43 years of disrespect.
She paid tribute to the perseverance of the families to pursue justice even though the State "abused its power to bully, intimidate, pressure and coerce heartbroken mothers, grieving fathers and devastated families".
"This travesty happened on the watch of successive governments," Ms McDonald added.
Fianna Fáil TD Seán Haughey, whose father Charles was Taoiseach at the time of the tragedy, said that "the decision to seek a new inquest was an inspired one".
Mr Haughey added that he is "in awe of the families" who fought on in "that dark time".
Earlier, Stardust survivor and campaigner Antoinette Keegan said the Taoiseach's State apology must be robust, sincere and address issues including the systematic abuse that the families have been subjected to for the last 43 years from the State.
"We should never had to go through the last 43 years," Ms Keegan said.
Speaking on RTÉ's Morning Ireland, Ms Keegan said she was 18 when the fire happened and her "whole life has been Stardust".
"My life has never been the same and that's one of the reasons why I could never give it up because over the last 43 years every time I went to different officials, ministers, taoiseachs, etc., and tell them my story, I was called a liar," she said.
"That didn't happen. That it's not in the Keane Tribunal."
She said that the families met with Mr Harris on Saturday and said he understands the "hurt and pain that they have gone through".
Ms Keegan said that she would like people to be taught about the Stardust tragedy and she told Mr Harris it should be put into the school curriculum.
It should have never ever happened, she said.
She paid tribute to the families' legal team without whom, she said, they would not be where they are currently.
Ms Keegan added that former RTÉ journalist Charlie Bird was "absolutely fantastic" and supported the families throughout the entire ordeal since 1981.
He was a "beautiful man and we sadly miss him today", she said.
The families of those affected by the Stardust tragedy must be "correctly and adequately compensated for what occurred" according to their solicitor Darragh Mackin.
Speaking on his way into Leinster House, he said discussions around redress have not yet taken place but will "in due course".
He said it must be an apology "on every front" and "must not just acknowledge the failings at the time, it must acknowledge forty years of failings that these families have been put through".
Stardust campaigner says life never the same since fire
State apologies
In February 2013, then Taoiseach Enda Kenny issued an apology on behalf of the Government in Dáil Éireann to women who were resident in Magdalene Laundries for hurt done to them and any stigma suffered by reason of their residence in those institutions.
In October 2019, then Taoiseach Leo Varadkar issued an apology in the Dáil on behalf of the State to the women and their loved ones affected by failings in the CervicalCheck screening programme.
The apology came on foot of Dr Gabriel Scally's scoping inquiry into CervicalCheck.
In January 2022, then Taoiseach and current Tánaiste and Minister for Foreign Affairs Micheál Martin issued a formal apology for the hurt experienced by many former residents of mother and baby institutions and county homes.
He apologised for the profound generational wrong visited on Irish mothers and their children who ended up in a mother-and-baby home or a county home and for the shame and stigma which they were subjected to.
In June 2018, on the 25th anniversary of the decriminalisation of homosexuality, a sincere apology was offered to those individuals affected by the criminalisation of homosexual acts in Ireland in an all-party motion in the Dáil.
Read/watch more:
Timeline: How the Stardust fire unfolded in 1981
Who were the 48 victims of the Stardust nightclub fire?
Fight for justice: The long road to the Stardust inquests
Watch: Remembering the night of the Stardust tragedy
