Events from the year 1799 in Ireland.

• Monarch: George III

• 24 January – A motion to debate an Act of Union is defeated in the Irish House of Commons, though it is later approved in the House of Lords
• 9 February – around 91 die when a barge capsizes at the bridge at Carrick-on-Suir.^[1]
• 15 February – the rebel guerilla leader Michael Dwyer escapes from a gun battle with British troops at Miley Connell's cottage, Dernamuck, in the Glen of Imaal, Wicklow. (today called the Dwyer–McAllister Cottage)^[2]
• River Shannon made navigable from Limerick to Killaloe.^[3]

• 28 February – William Dargan, engineer and railway builder (died 1867).
• 9 August – Henry Maxwell, 7th Baron Farnham, politician and peer (died 1868).
• 12 August – Patrick MacDowell, sculptor (died 1870).
• 22 December – Nicholas Callan, priest and scientist (died 1864).
• 26 December – William Kennedy, Scottish poet, journalist and diplomat (died 1871 in France).

  Full date unknown

  • Henry Archer, barrister and entrepreneur in north Wales (died 1863 in France).
  • Joseph M. Hawkins, Alamo defender (died 1836 in the United States).

• 11 January – Thomas Bermingham, 1st Earl of Louth (born 1717)
• 27 February – Sir John Blackwood, 2nd Baronet, politician (born 1722).
• 29 March – Charles Bingham, 1st Earl of Lucan, High Sheriff of Mayo in 1756 (born 1735)
• 4 June – Philip Woodroffe, surgeon
• 4 August – James Caulfeild, 1st Earl of Charlemont, politician, first President of the Royal Irish Academy, president of the volunteer convention in Dublin, 1783 (born 1728).
• 6 December – John Moore, participant in Irish Rebellion of 1798, proclaimed President of the Government of the Province of Connaught (born 1767).
• 11 December – "Brave" Charles Edward Jennings de Kilmaine, soldier in France (born 1751; died in France).