Louth is a parliamentary constituency represented in Dáil Éireann, the lower house of the Irish parliament or Oireachtas. The constituency elects 5 deputies (Teachtaí Dála, commonly known as TDs) on the system of proportional representation by means of the single transferable vote (PR-STV).

The constituency was created by the Electoral Act 1923, and first used at the 1923 general election.^[1] It currently spans the entire area of County Louth (which includes the towns of Ardee, Dundalk, Drogheda), the smallest county in Ireland, and parts of County Meath (suburbs of Drogheda and Laytown–Bettystown–Mornington–Donacarney). The boundaries were enlarged at the 2011 general election to include an area of County Meath adjacent to the town of Drogheda.^[2] This followed a recommendation of the Report of the Constituency Commission on Dáil and European Parliament Constituencies 2007 outlined "by extending the constituency southwards from, and in the environs of, Drogheda and taking in electoral divisions which have extensive linkages with the town. This will allow the inclusion of the town of Drogheda and hinterland areas in a single constituency." This revision also increased the number of seats to 5.^[3][4]

The Electoral (Amendment) (Dáil Constituencies) Act 2017 defines the constituency as:^[5]

"The county of Louth;

and, in the county of Meath, the electoral divisions of:

Julianstown, St. Mary's (part), in the former Rural District of Meath."

The Constituency Review Report 2023 of the Electoral Commission recommended that at the next general election, Louth should remain a 5-seat constituency, with the transfer of the electoral division of Julianstown to Meath East.^[6]

For the next general election, the Electoral (Amendment) Act 2023 defines the constituency as:^[7]

"The county of Louth;

and, in the county of Meath, the electoral division of:

St. Mary's (part), in the former Rural District of Meath."

Note: The columns in this table are used only for presentational purposes, and no significance should be attached to the order of columns. For details of the order in which seats were won at each election, see the detailed results of that election.

Louth population as per electoral division,^[53] for the Dáil constituency of Louth. This population count includes those within the county of Louth, as well as the electoral divisions of Julianstown, and St. Mary's (part) in the county of Meath, as per the Electoral (Amendment) (Dáil Constituencies) Act 2017.^[5]

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