Fine Gael's Gabrielle McFadden has been elected to the Dáil in the Longford-Westmeath by-election.
Ms McFadden won on the seventh count after Fianna Fáil's Aengus O'Rourke was eliminated.
Ms McFadden achieved a vote of 20,058 and was deemed to be elected without reaching the quota.
The by-election was called after sitting TD Nicky McFadden, a sister of Ms McFadden, passed away from Motor Neuron disease at the age of 51 in March 2014.
In the immediate aftermath of the death, it was not thought likely that the by-election would take place before the summer of this year.
However, in a move that surprised some observers, the Government decided instead to have the election - and the Dublin West by-election - on the same date as the Local and European Elections.
Ms McFadden is a Westmeath County Councillor based in Athlone and was elected Mayor of Athlone in 2013.
She was first elected in 2009, with 892 votes on the seventh count.
She withdrew from the local elections to concentrate on the by-election campaign.
Her election means that Fine Gael have two seats in the constituency, with the other being held by James Bannon.
Labour's Willie Penrose and Fianna Fáil's Robert Troy hold the other seats in the four-seat constituency.
Coppinger wins Dublin West by-election
Socialist Party candidate Ruth Coppinger topped the poll in the Dublin West by-election with 20.6% of first preference votes.
Ms Coppinger won on the sixth count after Fianna Fáil's David McGuinness was eliminated.
Ms Coppinger had a vote of 12,334, shy of the quota of 14,478 but sufficient to secure victory in the four-seat constituency.
The by-election was called after Patrick Nulty resigned after sending inappropriate messages over Facebook, including one to a 17-year-old girl.
Mr Nulty had been elected in an October 2011 by-election held to replace the late Brian Lenihan.
Ms Coppinger also contested the 2011 election and has served as a member of Fingal County Council since 2011.