US President Joe Biden declared he was home as he made a historic address to the Oireachtas where he spoke of the strength of the Irish-US relationship and promised a future of unlimited shared possibilities.
In his address, Mr Biden also said that "peace is precious" as he suggested the UK should be working more closely with Ireland to support Northern Ireland.
"Peace is precious. It still needs its champions. It still needs to be nurtured."
The Good Friday Agreement, he said, had a "significant positive impact across the Republic of Ireland as well".
Reflecting on discussions with Taoiseach Leo Varadkar, he spoke of "how Ireland and the United States can work together with the United Kingdom and the European Union to support the people of Northern Ireland".
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"I think that the United Kingdom should be working closer with Ireland in this endeavour. Political violence must never be allowed again to take hold on this island."
His remarks received applause from assembled politicians.
Tonight, President Biden attended a banquet dinner held in his honour at Dublin Castle and hosted by Taoiseach Leo Varadkar.
Among the guests were former taoisigh Micheál Martin, Bertie Ahern and Enda Kenny, as well as the leaders of Sinn Féin north and south, Mary Lou McDonald and Michelle O'Neill.
There were also representatives from across politics, sport and society.
Fourth US president to address Oireachtas
Mr Biden was the fourth US president to address the Irish Parliament after John F Kennedy in 1963, Ronald Reagan in 1984 and Bill Clinton in 1995.
The US president was today welcomed with sustained, rapturous applause as he entered the chamber to deliver a speech.
He opened his address by saying: "Well mom, you said it would happen."
Mr Biden went on to jokingly apologise to the infant daughter of Labour senator Rebecca Moynihan, who was in the chamber, for putting her through a policy speech, saying it is "as bad as what my children have been put through".
Asking to be forgiven for his attempt at speaking the Irish language, he said "Tá má seo (sa) abhaile" (I am home). He added: "I only wish I could stay longer."
Mr Biden praised the "enduring" strength of the Irish-US relationship as he promised "a future poised for unlimited shared possibilities".
He said: "The journeys of our ancestors expanded our horizons and literally excited our imaginations. They became the untiring backbone of America's progress as a nation, even as they endured discrimination and they were denied the opportunity."
Mr Biden appeared to reference an earlier gaffe, telling the Dáil chamber he has in the Oval Office a rugby ball signed by the Irish team from the game when they beat the All Blacks, after previously referring to the Black and Tans, before correcting himself.
He went on to recall a trip to Ireland with his family in 2016 when they explored their ancestry in the Cooley Peninsula.
President Biden recalled returning to Carlingford yesterday, and the view over Carlingford Lough, "likely one of the last glimpses of Ireland my Finnegan ancestors saw as they gazed on their way out in what in those days was referred to as a coffin ship".
He said Barack Obama's ancestors had sailed from the same port five weeks earlier, adding: "The idea they both sailed for a new life and thought their great-great-grandsons would both be president, I think, is really is a little bit of Irish malarkey."
He said talking about his Irish ancestry is "not to wax poetic about bygone days, but because of the story of my family's journey and those who left and those who stayed is emblematic of the stories of so many Irish and American families".
"These stories are the very heart of what binds Ireland and America together," he said. "They speak to a history defined by our dreams, they speak to a present written by our shared responsibilities, and they speak to a future poised for unlimited shared possibilities.
"Today I'd like to reflect on the enduring strength of the connections between Ireland and the United States, a partnership for the ages."
In his closing remarks to the Dáil, Joe Biden said: "This is one of the great honours of my career, to be here today, and I mean this from the bottom of my heart.
"Folks, I really mean it, we can do so much, we really can. It doesn't even break down on ideology, it breaks down on faith in ourselves, our values.
"Because no matter what party we belong to, our values are the same. It's about honesty, dignity, justice, and you all have every ingredient to make it work.
"It's an honour to be here, thank you very much," Mr Biden said.
Earlier, Mr Ó Fhearghaíl welcomed President Biden to the Dáil chamber before his address.
The Ceann Comhairle said that this "is the day we have looked forward to since your election as the 46th president of the United States just over two years ago".
Mr Fhearghaíl also extended "a very special and warm welcome to the much admired" Ukrainian ambassador to Ireland Gerasko Larysa.
He said Ms Larysa "represents the nearly 80,000 displaced Ukrainian citizens now resident" in Ireland.
Security was extremely tight around Leinster House in the run-up to the address.
TDs and Senators arriving this morning were asked to go through security scanners and post to the building has been restricted for the past forty-eight hours.
A host of special guests attended the address, including Marie Heaney, the widow of poet Seamus Heaney.
Former Taoisigh Bertie Ahern and Enda Kenny were also in the Dáil chamber.
Earlier, Mr Biden visited President Michael D Higgins at Áras an Uachtaráin.
He signed the visitors' book at a ceremony in the State reception room, quoting an Irish proverb "your feet will bring you where your heart is".
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Mr Biden then travelled across the Phoenix Park for a bilateral meeting with Taoiseach Leo Varadkar at Farmleigh House.
President Biden paid tribute to Ireland's role in welcoming Ukrainians fleeing war and hailed "stronger relations between the US and Ireland".
Northern Ireland, US-Irish ties, Ukraine and climate action were among the topics discussed by the Taoiseach and President during their bilateral meeting.
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