Lagan Valley assembly member Paul Givan has been announced as the DUP's nominee to be NI's new first minister.
Mr Givan would replace Arlene Foster, who was ousted as Democratic Unionist Party (DUP) leader in April after an internal revolt.
Edwin Poots, Stormont's agriculture minister, replaced her as DUP leader amid tensions within the party.
A number of DUP members have quit over concerns about the party's direction since Mr Poots' election last month.
Mr Givan had been widely tipped to replace Mrs Foster.
He was first co-opted to the Northern Ireland Assembly in 2010 and, aged 39, he will be Northern Ireland's youngest first minister.
Mrs Foster will remain as first minister until at least a meeting of the British-Irish Council in County Fermanagh on Friday. It is understood she will not remain in the post beyond Monday, but could leave sooner.
There is a seven-day period allowed for the approval of a first minister and deputy first minister by power-sharing partners Sinn Féin and the DUP.
Therefore, Mr Givan's nomination as first minister must be approved by Sinn Féin, which currently holds the position of deputy first minister.
Mr Givan said there was a "huge responsibility that comes with the position".
"We have a huge task when it comes to tackling our waiting lists and we need to get to work," he said.
"What we now need is an effective transition that needs to take place next week so that we have that smooth delivery of governance."
Mr Givan said it was a huge task to follow DUP founder Ian Paisley, and his successors Peter Robinson and Arlene Foster, whom he referred to as "giants".
On Tuesday, Mr Poots also made the following ministerial announcements:
- Foyle MLA Gary Middleton will be junior minister in the Executive Office
- Strangford MLA Michelle McIlveen will be education minister, replacing Peter Weir
- North Antrim MLA Paul Frew will be economy minister, replacing Diane Dodds
The three new ministers are due to take up their posts from Monday.
Who is Paul Givan?
Paul Givan was one of the early names to be tipped for the post of first minister in the eventuality of Edwin Poots winning the DUP leadership contest.
He has previously served as a special adviser to Mr Poots, both when he was minister for the former Department of Culture, Arts and Leisure and when he was environment minister.
His own assembly career began in 2010, when he was co-opted in the Lagan Valley constituency to replace Sir Jeffrey Donaldson, who became an MP.
Prior to his appointment as first minister, he was chairman of the Stormont Justice Committee, although he has now been replaced in that role by party colleague Mervyn Storey.
He became communities minister in 2016, with his time in the post cut short by the collapse of Stormont in January 2017.
Mr Givan found himself at the centre of a political row in 2016 over his decision to cut funding for an Irish language scheme.
He has also previously supported schools teaching the theory of creationism.
Mr Givan endorsed Mr Poots' bid for leadership of the DUP.
On Tuesday, Mr Givan's father, Alan, told BBC's Evening Extra programme that the announcement has come as a "shock".
"He's very young to be promoted to this position and it's something that we would fear, it's come a bit too early for him," he said.
"We just hope and pray that he makes a job of it. The responsibility that he has, and all the decisions, it's a lot of pressure on reasonably young shoulders."
There were not too many surprises in these announcements.
Seventeen posts in total were handed out today - three women were included. We think there are possibly three, maybe four, among the 17 who wanted Sir Jeffrey Donaldson to be DUP leader.
So this is Edwin Poots' attempt to reach out to the other side to try and heal the wounds, but as we have noted in the tweets from Diane Dodds and Peter Weir, it looks as if that mission has failed.
Speaking to some in the Donaldson camp, this has fallen far short of what was expected in terms of building bridges within the party.
As for Paul Givan, he knows his way around government, so Edwin Poots will see him as a safe pair of hands.
He is also of the same political DNA as Mr Poots. He has effectively been on the DUP leader's shoulder throughout his political career from the minute he joined Mr Poots' office as backroom staff when he was 18, all the way to today when Mr Poots handed him his dream job as first minister.
Although just 39 years of age, Mr Givan has experience of the corridors of power.
The ministerial appointments have been made against a backdrop of tension within the party over the manner in which Mrs Foster was ousted, and the direction of Mr Poots' leadership.
DUP councillors Glyn Hanna and Kathryn Owen have resigned, along with others in the party's South Down association.
Mr Hanna said there was a "culture of fear" in the party and claimed he witnessed "bullying" at last month's meeting of the DUP executive, during which Mr Poots' election as leader was ratified by party members.
He alleged that people who had put their hands up at the meeting in support of a secret ballot on the leadership were told to put them down.
That claim was backed up by party member Roberta McNally, who was also at the DUP executive meeting and has also resigned.
DUP deputy leader Paula Bradley, however, said she did not see that happening.
What has the political reaction been?
Mrs Dodds' tweet was retweeted by Mrs Foster and Sir Jeffrey Donaldson - who narrowly lost in the DUP leadership contest to Mr Poots - while Sir Jeffrey also retweeted Mr Weir's comments.
Justice Minister and Alliance Party leader Naomi Long said she and Mr Givan have at times had a "tense" relationship.
"We're not hostile to each other. We will have to work together and we have had to work together," Mrs Long told Evening Extra.
Mrs Long said the first minister's job is one of the "most difficult in politics".
"Even very shrewd political operators have at times struggled to keep things together in the executive," she said.
"I think if Paul approaches the job with a bit of humility, works with colleagues and the staff within the Executive Office, takes good advice from his officials, he will be as capable as anyone else to do it."
SDLP leader Colum Eastwood said the changing political personnel in the executive would make "no difference to the lives of people across Northern Ireland unless there is a marked change in approach to government".
"The faces may be changing but the people in power are still the same," he said.
"The DUP and Sinn Féin have been joint heads of government for 14 years.
"We have already started to see a lurch back to the same old politics of division and deadlock."
During a number of appearances in Stormont's Great Hall on Tuesday, Mr Poots also announced the following committee and assembly appointments:
- Deputy leader Paula Bradley will remain as Communities Committee chairwoman
- Gordon Lyons will be vice-chair of the Health Committee
- Jonathan Buckley and David Hilditch will be chair and vice-chair of the Infrastructure Committee
- William Irwin will be vice-chair of the Audit Committee
- Pam Cameron will be the chair of the Assembly and Executive Review Committee
- Meryvn Storey will be chair of Justice Committee
- Christopher Stalford continues as principal deputy speaker
- Tom Buchanan will be vice-chair of Procedures
- Keith Buchanan will be chair of the Finance Committee
- William Humphrey will be chair of the Public Accounts Committee