Leo Varadkar is to stand down as Taoiseach and as the leader of Fine Gael.
He's due to make an announcement at Government Buildings from midday.
Mr. Varadkar assumed the office of Taoiseach in June of 2017.
He has been a Fine Gael TD for the Dublin West constituency since 2007.
He's resigning as leader of his party with immediate effect, and will step down as Taoiseach when a successor is appointed.
A new Taoiseach will be elected when the Dáil resumes after the Easter break.
"Fulfilling"
Leo Varadkar says leading the country has been the "most fulfilling time" of his life: "When I became Party Leader and Taoiseach back in June 2017, I knew that one part of leadership is knowing when the time has come to pass on the baton to someone else.
"And then having the courage to do it. That time is now.
"So, I am resigning as President and Leader of Fine Gael effective today, and will resign as Taoiseach as soon as my successor is able to take up that office.
"I have asked our Party General Secretary and Executive Council to provide for the new Leader to be elected in advance of the Ard Fheis on Saturday, April 6th, thus allowing a new Taoiseach to be elected when the Dáil resumes after the Easter break.
"I know this will come as a surprise to many and a disappointment to some. I hope you will at least understand my decision. I know that others will, how shall I put it, cope with the news just fine. That is the great thing about living in a democracy.
"There is never a ‘right time’ to resign high office. However, this is as good a time as any - Budget 2024 is done, and negotiations have not yet commenced on the next one.
"The institutions of the Good Friday Agreement are working again, and our trading relationship with the United Kingdom, in the post-Brexit era, is settled and stable.
"The new Taoiseach will have a full two months to prepare for the Local and European Elections, and up to a year before the next General Election.
"Personal and political"
"My reasons for stepping down now are personal and political, but mainly political.
"I believe this Government can be re-elected. I believe my Party, Fine Gael, can gain seats in the next Dáil. Most of all, I believe that would be the right thing for the future of our country, continuing to take us forward. Protecting what we achieved and building on it.
"After careful consideration and some soul-searching, I believe a new Taoiseach will be better-placed than me to achieve that - to renew and strengthen the top team, to refocus our message and policies, and to drive implementation. After seven years in office, I am no longer the best person for that job.
"There are loyal colleagues and good friends contesting the Local & European Elections and I want to give them the best chance possible. I think they will now have a better chance under a new Leader.
"In standing aside, I can do so in the absolute confidence that the country and the economy are in a good place, and that my colleagues in the Government from all three parties, Fine Gael, Fianna Fáil and the Greens, and the Oireachtas will continue to work hard for the nation’s best interests.
"On a personal level, I have enjoyed being Taoiseach, Leader and a Cabinet member since March 2011. I have learned so much about so many things, met people who I would never have got to meet, been to places I would never have seen, both home and abroad. I am deeply grateful for it and would wholeheartedly recommend a career in politics to anyone considering it.
"However, politicians are human beings. We have our limitations. We give it everything until we can’t anymore and then we have to move on.
"I will, of course, continue to fulfil my duties as Taoiseach until a new Taoiseach is elected and will remain as a constituency TD for Dublin West."