1866 in Ireland

Events

• 28 January – the Midland Great Western Railway opens to Westport railway station.
• 22 June – Archbishop Cullen is elevated to the cardinalate as the first Irish Cardinal.
• 13 July – the sets out from Valentia Island on the second attempt to lay the transatlantic telegraph cable. Robert Halpin is master and William Thomson technical consultant.
• 14 October – St Peter's Church, Belfast, later to become the Roman Catholic Cathedral, is dedicated, although the building is incomplete.
• Maziere Brady retires as Lord Chancellor of Ireland, an office to which he was appointed in 1846.
• Alexandra College is founded at Milltown, Dublin by the Quaker Ann Jellicoe, the first women's college in Ireland to aim at a university-level education.

  Sport

• The first modern Irish Derby, created by the 3rd Earl of Howth, the 3rd Marquess of Drogheda and the 3rd Earl of Charlemont, is run at the Curragh Racecourse.
• The Ulster Yacht Club is revived at Bangor, County Down, on the initiative of Frederick Temple Blackwood, 5th Baron Dufferin and Claneboye.

  The Arts

• The ballad "Come Back to Erin" is composed by 'Claribel', the English songwriter Charlotte Alington Barnard.

  Births

• 5 February – Domhnall Ua Buachalla, member of 1st Dáil, Fianna Fáil TD, last Governor-General of the Irish Free State.
• February – Michael Egan, trade unionist, city councillor and Cumann na nGaedheal TD.
• 15 June – Charles Wood, composer.
• 13 July – Emily Winifred Dickson, gynaecologist.
• 16 August – Dora Sigerson, poet.
• 1 November – Cheiro, born William John Warner, astrologer.
• 3 December – Ethna Carbery, born Anna Johnston, writer and poet.
• 7 December – Maude Delap, marine biologist
• December – Thomas Byrne, recipient of the Victoria Cross for gallantry in 1898 at the Battle of Omdurman, Sudan.
• ;Full date unknown
• :*Éamon a Búrc, tailor and seanchaí.
• :*Master McGrath, greyhound.
• :*Bridget Sullivan, domestic housemaid for Borden family of Fall River, Massachusetts.

  Deaths

• 5 January – Augustus Warren Baldwin, naval officer and political figure in Upper Canada.
• 11 January – Gustavus Vaughan Brooke, actor.
• 17 January – George Petrie, painter, musician, antiquary and archaeologist.
• 4 March – Alexander Campbell, religious leader in Britain and the United States.
• 18 May – Francis Sylvester Mahony, humorist and poet .
• 26 October – John Kinder Labatt, brewer in Canada.
• 26 October – Patrick McHale, soldier, recipient of the Victoria Cross for gallantry in 1857 at Lucknow, India.
• ;Full date unknown
• :*Edward Eagar, lawyer and criminal transported to Australia, politician.