3 January – Tomás Óg Mac Curtain shoots and mortally wounds Detective Garda SíochánaJohn Roche in Cork city centre. He had been disarmed by Garda Pat Malone in 1935. On this occasion he is spared the death penalty in view of his father's history.
17 January – Enid (Captain Wibe) of neutral Norway sailing from Steinkjer to Dublin, 10 miles north of Shetland, goes to assist SS Polzella which has been torpedoed by German submarine U-25 which then shells and sinks Enid.
Cato (Capt. Richard Martin), British, from Dublin to Bristol, strikes a mine 2.5 miles west of Nash Point: 13 die, 2 survive.
9 March – trawler Leukos sunk by gunfire from U-38, north west of Tory Island – 11 dead.[1] (She may have moved between the surfacing U-boat and English trawlers, in the hope that the tricolour would protect her while the English escaped.)
10 March – City of Bremen rescues 33 crew of Amor (Dutch) in the North Sea.
24 May – first secret meeting to formulate 'Plan W', joint action in the event of a German invasion of Ireland, is held between Irish officials and British military in London.
27 May
The Churchill war ministry in London agrees to seek co-operation from de Valera and creation of an All-Ireland Council during "the present emergency".[4]
Uruguay of neutral Argentina sailing from Rosario to Limerick with 6,000 tons of maize, sinks with scuttling charges by U-37 160 miles from Cape Villano: 15 die, 13 survive.
10 June – Violando N Goulandris of neutral (at this time) Greece sailing from Santa Fe, Argentina to Waterford with a cargo of wheat is torpedoed by U-48 off Cape Finisterre: 6 die, 22 survive.
12 June – U-38 lands a German spy, Karl Simon, in Dingle. He is promptly arrested and interned for the duration.
20 July – City of Waterford (Capt. T. Freehill) shelled by submarine in North Atlantic but escapes.
30 July – Kyleclare rescues 52 survivors from Clan Menzies (British) off County Mayo coast.
1 August – collier Kerry Head bombed off Kinsale; she survives this attack, but see 22 October.
8 August
Operation Dove: Republicans Seán Russell and Frank Ryan embark from Nazi Germany on U-boatU-65 for infiltration into Ireland, but Russell will fall ill and die on the passage and the operation is abandoned.
16 August – Loch Ryan (Capt. J. Nolan) bombed off Land's End but survives.[1]
24 August – City of Waterford (Capt. T. Freehill) bombed in Irish Sea but survives.
26 August – five German bombs are dropped on County Wexford in a daylight raid. One hits the Shelbourne Co-operative Creamery in Campile killing three women.[6]
27 August – Lanahrone rescues 18 survivors from Goathland (British) off County Kerry coast.
Edenvale (Capt. N. Gillespie) machine-gunned by German plane off Waterford coast.[1]
27 September – Manchester Brigade torpedoed off the Aran Islands.
3 October – the German news agency announces that the German government is willing to pay compensation for dropping bombs on Dublin.[7]
22 October – Kerry Head (Capt. C. Drummond) bombed again: all twelve hands lost, in full view of watchers on Cape Clear Island.[1]
26–28 October – RMS Empress of Britain, serving as a troopship under the British flag, is bombed, torpedoed and sunk off the Donegal coast with the loss of 45 lives. At 42,348 GRT she is the war's largest merchant ship loss.
7 November – Éamon de Valera, speaking in response to Winston Churchill's statement, says that there can be no question of handing over Irish ports for use by British forces while they retain control of Northern Ireland.
11 November – Ardmore (Capt. T. Ford) strikes a mine off the Saltee Islands – 24 die.
4 October – Brian O'Nolan's first "Cruiskeen Lawn" humorous column is published in The Irish Times; from the second column he uses the pseudonym 'Myles na gCopaleen'. The original columns are composed in Irish. He continues writing the column until the year of his death, 1966.
October – The Bell, a liberal monthly magazine of literature and social comment, is established in Dublin by Peadar O'Donnell under the editorship of Seán Ó Faoláin.
Seán Ó Faoláin publishes his travelogue An Irish Journey and novel Come Back to Erin.
^ abcdefghijForde, Frank (2000). "Appendix 3: Beligerent Action against Irish Ships". The Long Watch: World War Two and the Irish Mercantile Marine (rev ed.). Dublin: New Island. ISBN 1-902602-42-0.
^Hull, Mark M. (2002). Irish Secrets. German Espionage in Ireland 1939–1945. Dublin: Irish Academic Press. ISBN 0-7165-2756-1.
^Wills, Clair (2007). That Neutral Island. London: Faber. ISBN 9780571221059.
^Militärgeographische Angaben über Irland. Berlin: Generalstab des Heeres, Abt. für Kriegskarten und Vermessungswesen (IV. Mil.-Geo.), 1940. OCLC 10934333.
^"Three Irish Girls Killed By German Bombs". The Irish Times. 27 August 1940.
^"German Compensation for Bombing at Campile". The Irish Times. 14 February 1946.
^Bourke, Marcus (1993). Murder at Marlhill: Was Harry Gleeson innocent?. Dublin: Geography Publications. ISBN 0-906602-23-8.
^"Bombs Fall in County Dublin". The Irish Times. 21 December 1940.
^ ab"Playography Ireland". Dublin: Irish Theatre Institute. Retrieved 5 April 2015.
^ abCox, Michael, ed. (2004). The Concise Oxford Chronology of English Literature. Oxford University Press. ISBN 0-19-860634-6.