Simon Harris will become Ireland's next taoiseach (prime minister).
Aged 37, he is the country's youngest ever leader.
His appointment follows Leo Varadkar's official resignation on Monday.
After a vote in the Irish parliament, he travelled to meet the president to be officially installed.
Leo Varadkar says the Republic of Ireland is a great country.
"We are free and prosperous and safe with huge opportunities for our citizens that would have been unimaginable in the past," he says.
"We are not a failed state, we are a great state, we should love it and protect and build on all that's been achieved since independence to make it better still."
Leo Varadkar says the 20 years he has spent in politics have been the most rewarding of his life.
“But today is the beginning of a new era for my party, a new chapter in my life and a new phase for this collation government," he says as he begins his speech.
Varadkar adds he will continue as a full-time constituency TD.
Image source, OireachtasProceedings have started in the Dáil as Leo Varadkar addresses TDs.
Click play at the top of the page to watch it live.
Image source, ReutersThe Dáil is convening to begin the process of electing a new taoiseach.
Simon Harris will be proposed for the role by Minister for Social Protection and Fine Gael deputy leader Heather Humphreys.
This will be seconded by junior minister Peter Burke who is widely tipped to be appointed a cabinet minister later today.
Harris is on course to win the support of up to 87 TDs with several independent TDs agreeing to back him, along with his coalition government colleagues.
Speeches are expected to be made by the government parties as well as the main opposition party Sinn Féin and other politicians, who are expected to call for a general election.
Harris is expected to make his way to the Irish president's official residence to be formally installed as taoiseach this afternoon.
TDs are beginning to gather in the chamber ahead of Tuesday's vote.
Image source, OireachtasAoife Moore
BBC Dublin Reporter
Image source, PA MediaSimon Harris has promised a “fresh” Fine Gael as the party enters its 13th year in government.
With housing and immigration top of mind for Irish people, Harris has already made big promises.
In his first party conference speech he said he would extend Help to Buy for a further five years.
Harris has promised to reduce the Universal Social Charge (USC) on low and middle-income earners and extend hot school meals to 150,000 more children and 900 more primary schools.
He has also promised an increase in the carer's allowance.
Harris will seek to revitalise the image of Fine Gael in those he chooses for cabinet too, with all the potential picks for ministers in their 30s or 40s.
In Northern Ireland, the incoming taoiseach, who has very little experience negotiating in the region, will seek to establish new relationships with the unionist community who at times had a tense relationship with his predecessor, Leo Varadkar.
Image source, ReutersLeo Varadkar, who officially resigned as taoiseach on Monday, was Ireland's youngest and first gay prime minister.
He served twice as taoiseach in coalition governments - first from June 2017 to June 2020 and then again from December 2022 to this month.
His first term was dominated by Ireland's response to Brexit and insistence that no "hard border" could be imposed between Northern Ireland and the Republic of Ireland.
His second term was beset by problems including a cost-of-living crisis exacerbated by the war in Ukraine.
In March, Mr Varadkar made the shock announcement that he was resigning, saying he felt he was no longer the right person for the job and cited "personal and political" reasons for the decision.
Image source, PAThe eldest of three children, Harris is the son of a taxi driver and a special needs assistant.
After going to school in Greystones, he studied journalism and French at Dublin Institute of Technology.
First elected as a councillor in 2009, he was elected as a TD (member of parliament) in 2011 aged 24.
He landed his first cabinet role as health minister in 2016, later serving in further education and justice portfolios.
Harris lives in his constituency with his wife Caoimhe and two children, describing parenthood as “the most important job I have and ever will have”.
Simon Harris was the only candidate to replace Leo Varadkar, who announced he would resign as taoiseach and Fine Gael leader last month.
Varadkar says he stepped down for both personal and political reasons.
After his announcement, cabinet ministers such as Helen McEntee, Paschal Donohoe and Heather Humphreys, supported Harris.
However, one high profile figure, Simon Coveney, announced he would step down.
Harris says he wants the government, a coalition between Fine Gael, Fianna Fáil and the Green Party, to run for a full term.
A general election is to be held by March next year.
Welcome to our live coverage as Simon Harris prepares to become the next taoiseach (Irish prime minister).
The 37-year-old, who has already succeeded Leo Varadkar as Fine Gael leader, will be Ireland’s youngest ever leader.
Follow us for updates and click play at the top of the screen for the latest video from Dáil Éireann (Irish parliament).