Events from the year 1812 in Ireland.

• 1 October – English balloonist James Sadler starts a balloon flight from Belvedere House near Mullingar in an attempt to cross the Irish Sea. He fails and almost drowns as a result.
• October – a storm washes away temporary barracks erected on Tuskar Rock for lighthouse construction, killing 14 workmen.
• Robert Peel, Chief Secretary for Ireland, introduces a mobile constabulary in Ireland, intended to be less partial than the yeomanry stationed in Ulster at this time, who are nearly all Orangemen.^[1]
• Landowner John D'Arcy is granted a patent to hold a market at his new town of Clifden.

• 14 May – Charles William Russell, Roman Catholic clergyman and scholar (died 1880).
• 19 May – Edwin Wyndham-Quin, 3rd Earl of Dunraven and Mount-Earl, peer (died 1871).
• 29 May – Thomas O'Hagan, 1st Baron O'Hagan, Lord Chancellor of Ireland (died 1885).
• 5 July – Frederick Edward Maning, writer and judge in New Zealand (died 1883).
• 12 July – C. P. Meehan, priest, poet and writer (died 1890).
• 4 November – James Alipius Goold, Roman Catholic Bishop and Archbishop of Melbourne (died 1886).

  Full date unknown

  • George Allman, naturalist, professor of natural history in Edinburgh (died 1898).
  • John Benson architect for Irish Industrial Exhibition, Great Industrial Exhibition (1853) and the 1855 Cork Opera House (died 1874)

• 25 April – Edmond Malone, Shakespeare scholar and literary critic (born 1741).
• 22 June – Richard Kirwan, scientist (born 1733).
• 2 August – Edward Smyth, sculptor (born 1749).
• 27 August – John Blaquiere, 1st Baron de Blaquiere, soldier and politician (born 1732).

  Full date unknown

  • Robert Owenson, actor and author (born 1744).

• 1812 in Scotland
• 1812 in Wales