Events from the year 1809 in Ireland.

• October – completion of the Military Road across the Wicklow Mountains.^[1]
• 21 October – Nelson's Pillar opened in Sackville Street, Dublin.
• The first Roman Catholic Magdalene asylum in Ireland is opened in Cork.^[2]
• Blessington Street Basin was opened as a small drinking water reservoir in the north inner city of Dublin in 1809, paid for by Dublin Corporation.^[3] The reservoir was initially named after King George III, and was fed from a 1km-long canal spur that came off the main Royal Canal to meet Broadstone railway station at a harbour in front of it.^[4] The ground alone, covering merely an acre, cost the Corporation £1,052-9s-2d.^[3]

• Jonah Barrington's Historic Anecdotes and Secret Memoirs of the Legislative Union between Great Britain and Ireland is published.
• Edward Bunting's A General Collection of the Ancient Music of Ireland is published.

• 1 May – Samuel Blackall, soldier, politician and second Governor of Queensland, Australia (died 1871).
• James Duffy, author and publisher (died 1871).

• 8 October – Arthur Gore, 2nd Earl of Arran, politician (born 1734).

• 1809 in Scotland
• 1809 in Wales