Unionists will not have a majority of the 18 seats in Westminster for the first time, following the UK general election.
It was a disappointing night for the DUP in particular as its deputy leader was ousted by Sinn Féin and the party lost out to the Alliance Party in North Down.
SDLP leader Colum Eastwood won in Foyle and Alliance Party deputy leader Stephen Farry took the North Down seat vacated by Sylvia Hermon.
Outgoing DUP MP Nigel Dodds says "it's important that the Northern Ireland Assembly is up and running as quick as possible" so that Northen Ireland politicians can have a role to play in Brexit negotiations #GE19 pic.twitter.com/3NpEpE3LBq— RTÉ News (@rtenews) December 13, 2019
The results are symbolically significant, as there are now more nationalist and republican MPs from Northern Ireland (nine) than unionists (eight), reversing the 11/7 split from the 2017 election.
However, it was not a positive poll for Sinn Féin overall.
Its vote fell everywhere else and it suffered an embarrassing reversal in Foyle, where outgoing MP Elishia McCallion was decisively beaten by Mr Eastwood with a 17,000-vote majority.
"We hear you loud and clear, we know you want someone to go to Westminster to fight your case, to stand up to Boris Johnson, to protect us from Brexit" - Colum Eastwood
The results will be seen as potential evidence of a shift towards more centre-ground politics in Northern Ireland - a trend that appears to be borne out by another positive showing for the cross-community Alliance Party.
- As it happened: Northern Ireland results
- Northern Ireland election quotes of the night
- Dodds loses Belfast seat, Farry wins North Down
The SDLP, which went into the election with no Westminster seats, picked up a gain in Belfast South, where the DUP's other defeated MP, Emma Little-Pengelly, was vanquished by Claire Hanna.
The results in North Down and Belfast North and South all came in constituencies where other pro-Remain parties had stepped aside to maximise the chances of a victory over a DUP Brexiteer.
"If you look at the votes you will find the greater number of people in Northern Ireland still want to remain within the UK - that to me is a very important point" - Arlene Foster
It was a damaging night for unionism overall, with the DUP's woes compounded by the Ulster Unionist Party suffering another series of poor results.
UUP candidate Tom Elliott missed out in Fermanagh and South Tyrone by an agonising 57 votes to Sinn Féin's Michelle Gildernew.
DUP leader Arlene Foster said she was hugely disappointed but rejected any suggestion that her leadership was under threat.
"It was very clear in both North Belfast and South Belfast that nationalism came together and decided they were going to get rid of Emma (Little-Pengelly) and Nigel (Dodds)," she said.
"We fought very hard against that but the numbers were against us in both constituencies."
She claimed that, while there might be more nationalist MPs than unionists, more votes were cast overall for pro-Union parties.
"If you look at the votes you will find the greater number of people in Northern Ireland still want to remain within the UK - that to me is a very important point," she said.
Thank you to everyone who voted DUP. To those who felt unable to support us yesterday, we're listening. I know you want to get NI moving again & have an Assembly to fix our schools & hospitals. I will be at the Talks on Monday. We need a willing partner though.— Arlene Foster (@DUPleader) December 13, 2019
The Conservative majority at Westminster means the DUP has also lost its influential role as kingmaker and, as a consequence, potentially any lingering hope of securing changes to the Brexit deal.
The DUP is vehemently opposed to Boris Johnson's Withdrawal Agreement, claiming it will create economic borders down the Irish Sea and weaken Northern Ireland's place within the union.
Mr Dodds' defeat by John Finucane in Belfast North represents the DUP's biggest wound of the night, with the long-standing MP, who led the party at Westminster, falling in the most high-profile contest of the election.
Mr Finucane said: "On a night like tonight, when it is all still very surreal, I can't help but think of my father and where we have come from, not just as a family but as a society as well."
His father, Pat Finucane, was murdered by loyalist paramilitaries in 1989.
Mr Dodds said it was clear that Brexit was going to happen with the prime minister's majority and it was important to restore devolved power-sharing at Stormont.
He added: "But Boris Johnson needs to understand that we must have a Brexit that ensures that it protects the integrity of the United Kingdom and is the best deal for Northern Ireland and that is something we will continue to work with the Government on in the days ahead."
Mr Eastwood said his victory demonstrated that people were keen for Northern Ireland to "get back to work".
"This is a story about the revival of the SDLP, but it's more about the message and desire of the people of our city and the people of the north generally," he said.
"We hear you loud and clear, we know you want someone to go to Westminster to fight your case, to stand up to Boris Johnson, to protect us from Brexit.
"You also want us to get back to work in Stormont; no more excuses will be accepted by the people of our city or by the people of Northern Ireland."
Mr Farry hailed his resounding win in North Down as a blow against Brexit and pledged to work in Westminster to frustrate the EU exit.
"This is a victory for the values that this constituency has been known for many years, those of moderation, rationalism and inclusion," he said.
He added: "They have come together behind a single cause, of sending out a very powerful message that the North Down area wants to Remain.
"We believe that there is no such thing as a good or sensible Brexit.
"Indeed, all forms of Brexit are damaging to the UK and to us in Northern Ireland, and in particular the Boris Johnson deal."
Sinn Féin President Mary Lou McDonald has described the election as having "changed the political landscape in Ireland, in Britain and in Europe".
Ms McDonald said voters had "clearly responded" to the anti-Brexit initiative.
Turning to the planned start on Monday of fresh political talks to revive power-sharing, Ms McDonald said her party was ready to work towards an agreement.
"Sinn Féin wants to see a successful conclusion of the talks established by the two governments and the political institutions restored on a credible and a sustainable basis," she said.
"I and our negotiating team stand ready to re-enter talks with the two governments and the other parties on Monday and we will work towards securing agreement on outstanding issues."