Voters in the Dublin Bay South constituency are going to the polling stations for the first time during the pandemic to elect a new TD to replace former Housing Minister Eoghan Murphy.
Polls are open from 7am and will remain open until 10.30pm tonight, with the results of the by-election expected to be known tomorrow evening.
There are 15 candidates putting themselves forward for election and have been canvassing since Mr Murphy resigned his seat in April.
A series of safety arrangements have been put in place, to ensure the by-election can be held in accordance with Covid-19 public health advice.
Voters have been reminded to adhere to public health measures in the first vote to be held in Ireland since the beginning of the Covid-19 pandemic.
Constituents have been asked to bring their own pens and pencils to the polling stations as part of efforts to reduce the spread of Covid-19.
Voters are being urged to vote during quieter periods, use hand sanitiser and there are perspex screens at the presiding officers' desks.
People are also being reminded not to linger inside or outside of polling stations.
Turnout this morning was described as "quite slow".
Labour Senator Ivana Bacik has become the frontrunner for the vacant seat, and is now the bookies’ favourite at 2/5.
Fine Gael Councillor James Geoghegan was the early favourite but has slipped back to 2/1.
Senator and former MEP Lynn Boylan has been chosen as the Sinn Féin candidate and is the outside bet at 7/1, according to bookmakers Paddy Power.
The housing crisis has become the major battleground in the contest.
Other candidates include Deirdre Conroy of Fianna Fáil, and Councillor Claire Byrne running for the Green Party.
The Social Democrats have chosen Sarah Durcan, while the People Before Profit candidate is Brigid Purcell.
Other candidates in Dublin Bay South are Justin Barrett (National Party), Jacqui Gilbourne (Renua), Mairead Toibin (Aontú) and independents Dolores Cahill, Peter Dooley, Mannix Flynn, John Keigher and Colm O’Keefe.
