Carwyn Jones has announced he is to stand down as the Welsh First Minister in the autumn.
The 51-year-old former barrister, from Swansea, made the announcement at the Welsh Labour conference in Llandudno on Saturday.
Earlier, Swansea East MP Carolyn Harris had won the election to become Mr Jones' deputy within the Welsh Labour party.
His decision to stand down will bring to an end his nine-year stint as First Minister, succeeding Rhodri Morgan in December 2009.
Stephen Kinnock, Labour MP for Aberavon, said: "Carwyn has been a brilliant leader of Welsh Labour, and an outstanding First Minister. Truly a giant of Welsh politics. We wish him well."
The decision comes months after Mr Jones referred himself to an independent inquiry over allegations of bullying at a senior level of the Welsh Government three years ago, following the death of assembly member Carl Sargeant in November.
Former minister Leighton Andrews has said that Mr Sargeant, who is believed to have taken his own life four days after being removed from his role as cabinet secretary for communities and children while facing allegations of inappropriate behaviour, was "unquestionably the target" of some of the behaviour and "toxic" atmosphere.
Mr Jones previously told assembly members that any issues brought to his attention at that time were dealt with, but leader of the Welsh Conservatives Andrew RT Davies suggested Mr Jones may have "misled assembly members" over his knowledge of bullying in the Welsh Government.
Mr Jones acknowledged "the darkest of times" in recent months, and thanked his children and wife Lisa - who he said had been seriously ill in the run-up to conference - for their support.
He told conference: "In any normal political career, you expect to be put through the ringer, and even have your integrity challenged.
"I don't think anyone can know what these last few months have been like. No-one that is, apart from Lisa and the kids.
"They have carried me through the darkest of times. I have asked too much of them, and it is time for me to think about what's fair for them.
"And so, this will be the last Welsh Labour conference I address as party leader.
"I intend - as I've always maintained - to be here to give every answer to every question. But I intend to stand down in the autumn, allowing for a new First Minister to take their place by the end of this year.
"At that point it will make sense to have a fresh start. For my family, for my party and for my country."
He added: "I am incredibly proud of what we have achieved together so far. The election victories. The landmark legislation. A better deal for nurses, for students and our businesses. Putting Wales on the map.
"We made the constitution exciting. Okay - maybe we didn't quite manage that.
"Over the last nine years I have lost my mother, just six days after I became First Minister.
"She was a great influence on me and she had a great talent of being able to talk to anybody and a healthy disdain of snobbery which I hope I've managed to follow.
"Running for the leadership in 2009 while she was terminally ill was one of the most difficult things I've had to do and she's missed by us all.
"To my children. Sorry for all the times I wasn't there and all the things I missed. It'll change in the future.
"And to you, my Labour family. Thanks for all your support. Without the doors you knock, without the leaflets you deliver, without the work you do in your communities I know I wouldn't have been given this opportunity."