There are 39 multi-member constituencies, that elect 160 TDs (members of parliament), to Dáil Éireann, Ireland's lower house of the Oireachtas, or parliament, by means of the single transferable vote, to a maximum term of five years.
Article 16.2 of the Constitution of Ireland outlines the requirements for constituencies. The total number of TDs is to be no more than one TD representing twenty thousand and no less than one TD representing thirty thousand of the population, and the ratio should be the same in each constituency, as far as practicable, avoiding malapportionment. Under the Constitution, constituencies are to be revised at least once in every twelve years in accordance with the census reports, which are compiled by the Central Statistics Office every five years; under the Electoral Act 1997, a Constituency Commission is to be established after each census. The Commission is independent and is responsible for the redrawing of constituency boundaries. Members of the five person commission must be a Judge of the Supreme Court, Court of Appeal or High Court as Chair, the Clerk of the Dáil, the Clerk of the Seanad, the Ombudsman, and the Secretary General of the . Any alterations in the constituencies do not take effect during the life of the Dáil sitting when a revision is made. Legislation is being drafted which would move the functions of constituency review to a permanent Electoral Commission
The electoral system for general elections is proportional representation by means of a single transferable vote (PR-STV). Similarly, PR-STV is used in European Parliament elections, while by-elections (where this is only one vacancy) and presidential elections use alternative vote. The constitution specifies that the minimum number of TDs returned for each constituency is three, but does not define the maximum number; however, electoral law specifies a maximum number of five TDs.
The 2017 report of the Constituency Commission, proposed several changes to Dáil constituencies. These changes were provided for by the , and came into effect at the 2020 general election. The total number of TDs increased by two to 160, while the number of constituencies was reduced by one to 39, as well as various boundary revisions.