A TD (plural TDanna in Irish; full Irish form Teachta Dála /ˌtjɒxtə ˈdɔːlə/, Irish: [ˈtʲaxt̪ˠə ˈd̪ˠɑːlˠə], plural Teachtaí Dála) is a member of Dáil Éireann, the lower house of the Oireachtas (the Irish Parliament). It is the equivalent of terms such as "Member of Parliament" (MP) or "Member of Congress" used in other states. The official translation of the term is "Deputy to the Dáil", although a more literal translation is "Assembly Delegate".
For electoral purposes, the country is divided into areas known as constituencies, each of which elects three, four, or five TDs. Under the Constitution, every 20,000 to 30,000 people must be represented by at least one TD. A candidate to become a TD must be an Irish citizen and over 21 years of age. Members of the judiciary, the Garda Síochána, and the Defence Forces are disqualified from membership of the Dáil.
Until the 31st Dáil (2011–2016), the number of TDs had increased to 166. The 2016 general election elected 158 TDs, a reduction of 8, pursuant to the passage of the Electoral (Amendment) (Dáil Constituencies) Act 2013.