The Rev Ian Paisley and Martin McGuinness have taken their pledges of office to become first minister and deputy first minister in the Northern Ireland Assembly.
The ministers who will run Northern Ireland in the devolved institutions were nominated in the first sitting of the Assembly in five years. Taoiseach Bertie Ahern and British Prime Minister Tony Blair are attending the historic ceremonies in Belfast.
The Rev Ian Paisley
Mr Ahern and Mr Blair were in the visitors' gallery of Parliament Buildings, Stormont, this morning to witness the creation of a powersharing government led by political polar opposites.
It is the first time that Northern Ireland will be run by a government in which all the main nationalist and unionist parties have agreed to operate power together.
"In politics as in life, it is a truism that no one can ever have 100 per cent of what they desire. They must make a verdict when they believe they have achieved enough to move things forward," Dr Paisley said.
He said Sinn Féin's acceptance of the rule of law met that test. "Support for all the institutions of policing has been a critical test that today has been met and pledged, word and deed.
"Recognising the significance of that change from a community that for decades demonstrated hostility for policing has been critical in turning the corner," the DUP leader said.
Earlier he heralded "a new beginning" for the North. "I believe we're starting on a road which will bring us back to peace and prosperity."
Mr McGuinness said it was a day of history. "What we're going to see today is one of the mightiest leaps forward that this process has seen in almost 15 years," he said.
"We know that this will not be easy and the road we are embarking on will have many twists and turns. "It is, however, a road which we have chosen and which is supported by the vast majority of our people," Mr McGuinness added.
Speaking at Stormont, Sinn Féin president Gerry Adams said today was "another significant landmark in the process of transforming life on this island.
"Today is a good day for Ireland. I want to thank and commend everyone who worked to achieve this."
"I want also to remember everyone who was hurt or killed in the conflict. Over the weekend I spent time in county Tyrone with families of IRA volunteers killed 20 years ago today at Loughgall. Days like today must be about ensuring that events like Loughgall are never visited on another generation.
"I genuinely believe that we are all shaping a real process of national reconciliation and building a new relationship between the people on this island and between Ireland and Britain. There are clearly many challenges ahead, but have no doubt that all these challenges can be overcome."
In the Assembly, Dr Paisley and Mr McGuinness affirmed their pledges of office, which includes support for the PSNI and the courts.
Unlike the first executive that followed from the 1998 Belfast Agreement, collective cabinet responsibility will apply in this government. In the first executive, DUP ministers functioned virtually autonomously and refused to sit in the executive with Sinn Féin ministers.
Martin McGuinness speaking to members of the media this morning.
In contrast, both Dr Paisley and Mr McGuinness have agreed a busy programme of work for the days and weeks ahead.
In addition to the Taoiseach and British prime minister, several dignitaries are attending today's events, including US senator Edward Kennedy, asked by the White House to represent President Bush.
Mr Ahern and Tánaiste Michael McDowell flew to Belfast on the Government jet. Former PD minister of state Liz O'Donnell said she expected they would talk about the Taoiseach's finances in the margins of events at Stormont.
Minister for Foreign Affairs Dermot Ahern and Attorney General Rory Brady are attending the powersharing ceremony today.
Former taoisigh Albert Reynolds and John Bruton were also among those invited to join the Taoiseach's delegation, along with former tánaiste Dick Spring, former foreign minister David Andrews, and former government adviser on Northern Ireland, Senator Martin Mansergh.
Fine Gael leader Enda Kenny and Labour leader Pat Rabbitte are not on the Taoiseach's list, but spokesmen for both of them said last night they were "not making an issue of it".
The new powersharing government includes the DUP deputy leader Peter Robinson as Finance Minister, Sinn Féin's Caitriona Ruane as Education Minister, the DUP's Nigel Dodds as Economy Minister, Ulster Unionist leader Sir Reg Empey as Employment and Learning Minister, the SDLP's Margaret Ritchie as Social Development Minister, Sinn Féin's Conor Murphy as Regional Development Minister, the DUP's Arlene Foster as Environment Minister, Ulster Unionist Michael McGimpsey as Health Minister, Sinn Féin's Michelle Gildernew as Agriculture Minister and the DUP's Edwin Poutts as Culture Minister.
Assembly members are mourning the death of Democratic Unionist MLA George Dawson. Proceedings were adjourned for a short time as a mark of respect at 10.30am just after they began.