Taoiseach Brian Cowen has extended his congratulations to the new US president Barack Obama, who was sworn in at an inauguration ceremony in Washington DC today.
"Today is a day of joy and celebration in Washington, across the United States and across the world," he said.
"The inauguration of President Obama marks a new chapter in history and a new beginning for America. His inaugural address offered inspiration and hope to us all.
"As we face the great challenges that confront us, his leadership will be central to global economic recovery and to the advancement of peace and justice. On behalf of the people of Ireland, I offer President Obama our warmest congratulations, best wishes and support."
Fine Gael Leader Enda Kenny said the new president's election offered "hope to the global community with his commitment to re-engage positively with nations across the world".
“President Obama has already shown himself to be a charismatic leader with the drive and vision necessary to bring about real change.
“His historic inauguration today was rightly celebrated across the United States and the hope that his election has engendered will be felt far beyond America’s borders. The president’s inauguration address made it clear that he intends to re-engage with the global community. In a time of economic turmoil where peace is threatened throughout the world, President Obama’s words offer hope and his commitment is very welcome."
Mr Kenny said the new president faced "colossal challenges" but he was certain he would "be able to meet every problem that faced him.
Labour Party leader Eamon Gilmore also passed on his congratulations to Mr Obama. He said that this had been a historic day for the United States and a day of hope for all the world.
"During the extended presidential campaign and since his election Barrack Obama has shown himself to be a leader with a clear political vision and an ability to mobilise and inspire a whole new corps of voters and political workers," he said.
"Barack Obama has created a huge level of expectation. He faces immense problems at home and abroad. I hope that he can now meet those expectations and I wish him every success in his period in the White House," he added.
Sinn Féin President Gerry Adams, who attended Mr Obama's inauguration in Washington, welcomed the new US president's "Very positive" speech.
"He is clearly signalling his determination to tackle the many challenges facing the US people as well as a change in US Foreign policy and on the environment. It was a great honour to be present at the inauguration," Mr Adams said.
"His words were obviously very uplifting to the American people assembled here. In fact my big memory of today will be about the cheerfulness, sense of purpose and positive attitude of everyone I met. The huge crowd of people from very obvious different ethnic backgrounds had a clear sense of the history of this inauguration - 150 years after the inauguration of Abrham Lincoln and the day after Martin Luther King Day."
"We are assured that President Obama will continue the US policy of encouraging and supporting the process of change in Ireland. As we who live on the island continue to make progress people's minds will turn logically to the issue of unity and an end to division in our country. Sinn Féin will certainly be doing our best to achieve that."