A dozen candidates are contesting the Cork North Central by-election to fill the Dáil seat vacated by Fianna Fáil's Billy Kelleher, following his election to the European Parliament in May.
There is an electorate of just over 85,000 people and the constituency boundary has not changed since the 2016 General Election.
Turnout in Cork North Central in that election was just over 63%, however it is expected to be substantially less than that in this by-election.
Polls opened at 141 booths at 7am.
Of the 12 candidates contesting the by election, two are female and ten are male.
Half the candidates are already elected representatives: one senator, four city councillors and one county councillor.
Roughly speaking, the constituency extends over the north side of Cork city, from the north channel of the River Lee, to the suburbs of Glanmire in the east, parts of Bishopstown in the west and Blarney in the north.
It contains an urban and rural mix, and the issues highlighted during the campaign are reflective of this - with questions on housing and homelessness, pressure on farming and rural decline.
Sorting and counting of votes will begin tomorrow morning at Nemo Rangers GAA Club.
A result is expected by late afternoon.
