Tom Elliott has taken Michelle Gildernew's seat in Fermanagh and South Tyrone as three outgoing MPs in Northern Ireland lost their seats in the Westminster election.
Ms Gildernew of Sinn Féin lost out to Mr Elliott of the Ulster Unionist Party by 530 votes, 1% of the vote for the constituency.
Ms Gildernew had won the traditionally close seat by four votes in 2010, a margin that was reduced to a solitary ballot paper after review by the electoral courts.
Mr Elliott, a former UUP leader, was one of four candidates which the UUP and the Democratic Unionists agreed upon in order to maximise the Unionist vote.
Ukip and the Traditional Unionist Voice also did not run candidates, effectively giving Mr Elliott a clear run.
Sinn Féin President Gerry Adams said the unionist pact was held together by an "opposition to change, opposition to equality and in support of a union that is imposing austerity."
In his speech, Mr Elliott said the constituency, which is the most westerly one in the UK is "not a green constituency".
Mr Elliott added the seat "does not belong to Bobby Sands, it belongs to the people of Fermanagh and South Tyrone and that is who I intend to represent".
Sinn Féin requested a recount, but the returning officer refused the request due to the size of the margin.
Meanwhile, the first surprise result of the entire election came in South Antrim, where Danny Kinahan of the Ulster Unionist Party took the DUP seat held by William McCrea by 949 votes.
The seat was the first in the entire election to change hands.
Mr Kinahan, a former army officer, said he is humbled to be elected, describing it as an "immense pleasure".
Mr Kinahan, who said in his speech that "we have to have a fair and equal society", was the only Ulster Unionist or DUP assembly member to vote for same-sex marriage in the Northern Assembly.
However, the DUP will not be weakened by the loss of Mr McCrea's seat thanks to Gavin Robinson, who successfully took Belfast East from Naomi Long of the Alliance Party.
Mr Robinson had over 2,500 votes to spare over Ms Long, topping the poll with 19,575, compared to the 16,978 votes for the Alliance Party's only outgoing MP.
The electoral pact between the two main Unionist parties meant the UUP did not run a candidate in the constituency which DUP leader Peter Robinson lost in 2010.
Ms Long wished Mr Robinson well, saying it was a privilege to represent the people of east Belfast.
She also said the DUP would not have taken the seat if the pact was not in place.
The DUP has maintained the eight Westminster seats it won in 2010, with Mr McCrea the only DUP MP to lose their seat.
Party leader Peter Robinson has said the party does not want to be in a coalition, but wants to get the best deal possible for Northern Ireland.
Exit polls had suggested the Conservatives were in line to take 316 seats, however, David Cameron's party eventually secured a parliamentary majority in the House of Commons, taking 326 seats.
Sinn Féin has taken four seats - in Belfast West, Newry and Armagh, Mid-Ulster and West Tyrone - one seat less than the party won in 2010
The SDLP successfully held onto the three seats in Belfast South, Foyle and South Down which they won in 2010
The UUP has taken two seats, a clear improvement on its 2010 whitewash, through Mr Kinahan in South Antrim and Mr Elliott in Fermanagh and South Tyrone.
Independent Unionist MP Sylvia Hermon took the remaining seat in North Down.
Ms Long's defeat means the Alliance Party is without representation in Westminster.
Jeffrey Donaldson, the outgoing MP for Lagan Valley, received 19,055 valid votes and was the first MP deemed elected in Northern Ireland.
Alexander Redpath of the Ulster Unionist Party was second in the constituency with 6,055 as Mr Donaldson increased his majority by almost 1,000.
Mr Donaldson said: "We are so successful here because we don't take people for granted."
Ian Paisley Jr topped the poll for North Antrim with 18,107 votes.
The son of the late DUP founder was comfortably clear of Timothy Gaston of the Traditional Unionist Voice.
In his speech, Mr Paisley said Ulster MPs could have a say in the incoming government.
In Strangford, Jim Shannon also retained his seat, topping the poll with 15,053 votes.
Prior to the result, Mr Shannon said the party may seek cooperation with the Conservatives rather than a coalition.
The UUP and the Alliance Party polled second and third in the constituency.
Mr Shannon's party colleague David Simpson, who was expected to face a tough challenge from the UUP's Jo-Anne Dobson, topped the poll for Upper Bann.
Mr Simpson took the seat from former UUP leader David Trimble ten years ago, and held onto it by 2,264 votes ahead of Ms Dobson.
After the declaration Mr Simpson slammed what he described as "a despicable attack" on his family on social media.
Sammy Wilson was re-elected for the DUP in East Antrim with 12,103. Roy Beggs of the UUP was second with 6,308 votes.
Speaking prior to the declaration, Mr Wilson, who has held the seat since 2005, said his party had "objectives which we wish to achieve to improve the lives for all of the people in Northern Ireland, to improve the economy in Northern Ireland, to improve public services, to ensure there is fairness and equality and to strengthen the Union."
Nigel Dodds, the DUP's leader in Westminster in the previous term, topped the poll in Belfast North.
The Unionist electoral pact ensured Mr Dodd's safe passage back to Westminster, with the UUP not running a candidate in the constituency.
In his speech, Mr Dodds said it was one of "the nastiest campaigns" he had been involved in.
Mr Dodds claimed Sinn Féin engaged in sectarian tactics and dirty tricks in an attempt to oust him.
However, he hailed the electorate for delivering the DUP its largest-ever vote in the constituency to see off the challenge of Sinn Féin veteran Gerry Kelly.
Mr Dodds had claimed an election leaflet circulated by Sinn Fein was sectarian and accused the party of being behind a letter sent to unionist voters making what he insisted were false claims about his record as an MP.
Gregory Campbell was also re-elected in East Londonderry, ensuring that the DUP retained the eight seats they won in 2010 with no candidate running in either of the remaining constituencies.
Mr Campbell received 14,663 votes, comfortably clear of Caoimhe Archibald on 6,859.
Mr Campbell's seat was never in doubt, but the Unionist stalwart was delighted to increase his share of the vote to 42%
Francie Molloy, Sinn Féin's MP for Mid-Ulster was also re-elected, taking 19,935 votes - 13,617 votes ahead of Sandra Overend.
Mr Molloy first took the seat in a by-election three years ago after Martin McGuinness stood down.
Mickey Brady, a relative newcomer who was first elected to the Northern Ireland Assembly in 2007, topped the poll in Newry and Armagh with 20,488 votes.
Mr Brady took the seat from party colleague Conor Murphy, who had held it since 2005.
Former Armagh footballer and All-Ireland winner Justin McNulty, representing the SDLP, was third in the poll.
In West Tyrone, Sinn Féin's Pat Doherty topped the poll with 16,807 and was re-elected to serve a fourth term.
Mr Doherty, first elected in 2001, had more than 10,000 votes to spare over Tim Buchanan of the DUP.
Paul Maskey was the second Sinn Féin MP returned, comfortably taking the Belfast West seat with 19,163 votes.
People Before Profit's Gerry Carroll came second in the constituency, winning 6,798 votes.
The SDLP's Mark Durkan was re-elected for the Foyle constituency with 17,725 votes.
Gearóid Ó hEára of Sinn Féin came second with 11,679 votes.
Mr Durkan's party leader Alasdair McDonnell also retained his seat in Belfast South, topping the poll with 9,560 votes.
Mr McDonnell had less than 1,000 votes to spare over Jonathan Bell of the DUP.
Mr McDonnell said "the SDLP remains committed to opposing the Tory agenda and ensuring that we get the best possible deal for Northern Ireland".
The SDLP is a sister party of the Labour Party, but Mr McDonnell has said it would make its own mind up and has called for a "prosperity process" to support the peace process.
Margaret Ritchie took the SDLP's third seat in South Down, ensuring they maintained the same parliamentary presence from 2010.
Ms Ritchie took 18,077 votes, almost 6,000 ahead of Chris Hazzard of Sinn Féin.
Independent MP Sylvia Hermon, widow of former RUC chief constable John Hermon, was the clear winner in North Down, securing 17,689 votes.
Ms Hermon, who is a former member of the UUP, earlier said she will be "amazed if David Cameron comes calling" looking for her support.
Ms Hermon added herself and Mr Cameron have not always exchanged Christmas cards and she does not expect a call at the weekend.
Speaking on RTÉ News before the declarations, Sinn Féin's Gerry Adams said if David Cameron's Conservatives are returned to government, the promised referendum on EU membership could have profound consequences for the island of Ireland.
He said he has called on Taoiseach Enda Kenny to engage with Mr Cameron if this situation comes to pass.
Mr Adams added that his other great concern is the impact of the Conservative's austerity policies on the people of Northern Ireland and on the Stormont executive.
