Events from the year 1843 in Ireland.

• January – Daniel O'Connell proclaims 1843 as the "Repeal Year".^[1]
• 31 January – Queen's Bridge in Belfast opens.^[2]
• 21 February – repeal (of the Act of Union) debate in Dublin Corporation.^[1]
• 17 March – earthquake in the Irish Sea.^[3]
• 11 June
  • Series of monster meetings to agitate for repeal begins at Tuam.^[1]
  • O'Connell's "Mallow defiance".^[1]
• 15 August – repeal meeting at Tara.^[1]
• 17 August – Loreto Abbey, Dalkey opened as a girls' boarding and day school by the Sisters of Loreto.
• 18 August – Dalkey Atmospheric Railway opens unofficially.
• 7 October – O'Connell gives in to government prohibition of Clontarf meeting planned for the next day. However, he is charged with conspiracy a few days later.^[1]
• November – Devon Commission appointed to research the problems with land leases.^[1]
• Work starts on the building of Crumlin Road Prison in Belfast.
• George Cannock and Andrew White establish the Dublin business that becomes Arnotts department store.

• Charles Lever's novel Arthur O'Leary: His wanderings and ponderings in many lands is published serially in Dublin University Magazine and Tom Burke of Ours begins serial publication in Dublin.

• 11 January – C. Y. O'Connor, engineer in Australia (died 1902).
• 3 May – Edward Dowden, critic and poet (died 1913).
• 14 August – Thomas Workman, entomologist and arachnologist (died 1900).
• 6 November – William James Craig, Shakespearean scholar (died 1906).
• 24 November – Richard Croker, politician in America and a leader of New York City's Tammany Hall (died 1922).
• 21 December – Thomas Bracken, poet (died 1898 in New Zealand).
• 25 December
  • Albert Cashier, born Jennie Hodgers, soldier in the Union Army during the American Civil War, lived as a man (died 1915 in the United States).
  • George Fisher, Mayor of Wellington (died 1905 in New Zealand).
• 28 December – George Thomas Stokes, ecclesiastical historian (died 1898).
• Full date unknown – Joanna Hiffernan, artists' model (died after 1903).

• 19 February – Michael Joseph Quin, author, journalist and editor (born 1796).
• 11 May – William Vesey-FitzGerald, 2nd Baron FitzGerald and Vesey, politician and statesman (born 1783).^[4]
• 10 August – Robert Adrain, scientist and mathematician in America (born 1775).
• 16 November – Abraham Colles, professor of Anatomy, Surgery and Physiology at the Royal College of Surgeons in Ireland (born 1773).
• 21 December – Edward Bunting, musician (born 1773).

• 1843 in Scotland
• 1843 in Wales