Captain Con Murphy from near Millstreet, County Cork was executed by British authorities, the first man to be executed in front of a firing squad since the 1916 Easter Rising.
5 March – Irish War of Independence: Clonbanin Ambush: The Irish Republican Army killed Brigadier General Hanway Robert Cumming.
16–17 March – Irish War of Independence: The Irish Republican Army killed two Royal Irish Constabulary constables in Clifden. The Black and Tans were called in and killed one civilian, seriously injured another, burned 14 houses and damaged several others.[1]
19 March – Irish War of Independence: Crossbarry Ambush: British troops failed to encircle an outnumbered column of Irish Republican Army volunteers in County Cork, with at least ten British and three IRA deaths.
21 March – Irish War of Independence: Headford Ambush: The Irish Republican Army killed at least nine British troops.[2]
25 May – Irish War of Independence: The Irish Republican Army occupied and burned The Custom House in Dublin, the centre of local government in Ireland. Five IRA men were killed and over eighty captured by the British Army which surrounded the building.[5]
20 June – Irish War of Independence: British Major-General Lambert died at Athlone of a gunshot wound sustained in an IRA ambush; early on 2 July six farmhouses in the area were burned, apparently in retaliation, and the following day the IRA, in turn, burn down Moydrum Castle.[6][7]
4 July – James Craig refused to attend a peace conference in Dublin because the invitation by President Éamon de Valera was addressed to him personally instead of to the Prime Minister of Northern Ireland.
10 July – Bloody Sunday: Clashes between Catholics and Protestants in Belfast resulted in 16 deaths (23 over the surrounding four-day period) and the destruction of over 200 (mostly Catholic) homes.[9]
11 July – Under the terms of the truce (signed on 9 July) which became effective at noon, the British Army agreed that there would be no provocative display of forces or incoming troops. The Irish Republican Army agreed that attacks on Crown forces would cease.
21 July - The Belfast Pogrom began with the one-day removal of thousands of Belfast shipyard, factory and mill workers from their jobs.
16 August – Following the uncontested election for the Parliament of Southern Ireland, 125 Sinn Féin teachtaí dála assembled as the Second Dáil at the Mansion House in Dublin. Six represented constituencies in Northern Ireland (five of them jointly with constituencies in the South).
23 August – The Northern Cabinet agreed that Stormont Castle would be the permanent site of the Northern Houses of Parliament.
8 September – Lloyd George's final offer was delivered to Éamon de Valera. Sinn Féin was invited to discuss the proposals which would grant limited sovereignty within the British Empire.
1 November – Frances Kyle and Averil Deverell were called to the Bar of Ireland, becoming the first female barristers in Britain or Ireland.
6 December – Agreement was reached in the Anglo-Irish Treaty negotiations in London. The main points included the creation of an Irish Free State within the Commonwealth, an Oath of Allegiance to the Crown, and retention by the British naval services of the use of certain Irish ports.
December – Éamon de Valera accused the Irish delegation to London of having ignored its instructions. Arthur Griffith accused de Valera of knowing at the time that a Republic could not be achieved.
24 February – Terence MacSwiney's play The Revolutionist (set and published in 1914) had its stage premiere posthumously at the Abbey Theatre.[11] His writings Principles of Freedom were collected from Irish Freedom (1911–12) and published this year also.
Ina Boyle's pastoral for orchestra Colin Clout premiered.
George Moore published the novel Heloise and Abelard.
L. A. G. Strong published the poetry Dublin Days (in Oxford).
^Villiers-Tuthill, Kathleen (2006). Beyond the Twelve Bens — a history of Clifden and district 1860-1923. Connemara Girl Publications. pp. 177, 209–213. ISBN978-0-9530455-1-8.
^O'Halpin, Eunan & Ó Corráin, Daithí (2020), The Dead of the Irish Revolution, Yale University Press, pgs 350-352
^Statutory Rules & Orders published by authority, 1921, No. 533
^Jackson, Alvin (2004). Home Rule – An Irish History. Oxford University Press. p. 198.
^Foy, Michael T. (2006). Michael Collins's Intelligence War: the struggle between the British and the IRA, 1919–1921. Stroud: Sutton. pp. 214–218. ISBN0-7509-4267-3.
^Ward, Alan J. (1994). The Irish Constitutional Tradition: Responsible Government and Modern Ireland 1782–1922. Washington, D.C.: Catholic University Press of America. pp. 103–110. ISBN0-8132-0793-2.