6th century in Ireland
500s
;506
- 23 March - Death of Bishop Mac Cairthinn of Clogher.{{cite book|editor1=Moody, T. W. |editor2=Martin, F. X. |editor3=Byrne, F. J. |title=A New History of Ireland. 8: A Chronology of Irish History|series=A Companion to Irish History, part I|publisher=Oxford University Press|year=1989|isbn=978-0-19-821744-2}}[https://celt.ucc.ie/publishd.html List of Published Texts at CELT] — University College Cork's Corpus of Electronic Texts project has the full list of Irish Annals.
;507
- Death of Lugaid mac Lóegairi, High King of Ireland.
- 3 September - Death of St. Mac Nisi, Bishop of Connor (according to some sources, see 509 below).
;509
510s
;512
- 29 June - A solar eclipse is recorded.
- 2 November - Death of Bishop Erc of Slane (according to some sources; see 513 below).
;513
- 2 November - Death of Bishop Erc of Slane (according to some sources; see 512 above).
;515
- Birth of Abbot Cainnech of Aghaboe at Glengiven near Dungiven in Ulster (according to some sources; see 516 below).
;516
- Battle of Druim Derge in Leinster; the Laigin finally lose the Irish Midlands to the Uí Néill.
- Birth of Bishop Ciarán of Clonmacnoise ("Ciarán the Younger"), one of the Twelve Apostles of Ireland.{{citation|last=Gratton-Flood|first=W. H.|title=The Twelve Apostles of Erin|work=The Catholic Encyclopedia|volume=I|location=New York|publisher=Robert Appleton Company|year=1907|url=https://www.newadvent.org/cathen/01632a.htm|access-date=2008-02-09}}
- Birth of Abbot Cainnech of Aghaboe at Glengiven near Dungiven in Ulster (according to some sources; see 515 above).
;517–518
520s
;520
- Monastery founded in Ballyleague by St. Faithleach of Clontuskert (brother of Brendan).{{cite web|title=Annals of Cloontuskert Parish|url=http://www.esatclear.ie/~annals|access-date=2013-02-01|archive-url=https://web.archive.org/web/20130227000413/http://www.esatclear.ie/~annals/|archive-date=2013-02-27|url-status=dead}}
- Clonard Abbey in modern County Meath founded by St. Finnian of Clonard.
- 3 May - Death of Conleth, Bishop of Kildare (in 516 according to some sources).
- (approximate year) - Clane Friary founded by Ailbe of Emly
;521
- 7 December - Birth of Columba (Colm Cille or Columcille) in Gartan, missionary monk (died 597).
- 7 December - Death of St. Búite of Monasterboice.
;522
- Death of Eochaid mac Óengusa,Annals of Tigernach. an Eoganachta king of Munster. His son Crimthann Srem mac Echado succeeds him.
;523
- St. Ninnidh made the island of Inishmacsaint (island of plain Sorrell) in Lough Erne his headquarters around 523.
;523–526
- 1 February - Death of St. Brigit of Kildare (year varies according to sources) (born c.451).
;527
- Death of Illan mac Dúnlainge, King of Leinster.
;527–528
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 534 or 542).
530s
;530
- Brendan completes building of monastic cells at Ardfert
- Monastic settlements are established on Lambay Island and at Clonmore, County Carlow.
- Birth of Dallán Forgaill, Ollamh Érenn, on Magh Slécht.
- Birth of Saint Moluag in Dál nAraidi.
- Death of Saint Cainnear of Bantry
- Approximate date - Death of St. Enda of Aran.
;531 (or 537)
;
- Maine mac Cearbhall, 1st King of Uí Maine, died 531 or 537.
;534
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 527, 528 or 542).
;535
- Possible mega-eruption of Rabual caldera volcano between {{nowrap|{{circa|535|540}}}}.
- Extreme weather events
- 20 August - Death of St. Mochta of Louth (disciple of St. Patrick) (in 537 according to some sources).
;536
- Extreme weather events causes Late Antique Little Ice Age
- Irish Annals record famine in Ireland.
;537
- Late Antique Little Ice Age
- A plague strikes Britain and Ireland.
;538
- Late Antique Little Ice Age
- Irish Annals records famine in Ireland.
- Death of missionary Manchan of Mohill.
;539
- Late Antique Little Ice Age
- Irish Annals records famine in Ireland.
540s
;540
- Birth of Columbanus at Nobber in the Kingdom of Meath.
- Approximate date - The Paschal controversy begins in Ireland.
;542
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 527, 528 or 534).
;545
- Monastery founded at Clonmacnoise{{cite book|title=Illustrated Dictionary of Irish History|editor=Mac Annaidh, Séamas|publisher=Gill and Macmillan|location=Dublin|year=2001|isbn=0717135365}} by St. Ciarán.
;546
- Columba founds Derry.
- Approximate date - Death of Abbot Ciarán of Clonmacnoise (of yellow fever) (according to some sources - see 556 below).
;549
- Roman Catholic Diocese of Ossory, which still exists, founded.
- Death of St. Finnian of Clonard, who founded Clonard Abbey.
550s
;550
- Birth of Bishop Máedóc of Ferns (St. Áedan or Mogue) on Magh Slécht.
;552
- Death of St. Finnian of Clonard, founder of Clonard Abbey.
;556
- Death of Abbot Ciarán of Clonmacnoise (of yellow fever) (according to some sources - see 546 above).
;557
- Death of the probably legendary Colmán Már mac Diarmato, a king of Uisnech{{cite book|title=The Chronology of the Irish Annals|first=Daniel P.|last=McCarthy|location=Dublin|publisher=Royal Irish Academy|year=1998|series=Proceedings of the Royal Irish Academy, Section C, Archaeology, Celtic studies, history, linguistics, and literature, 98(6)}} in Mide of the Clann Cholmáin.
560s
570s
;570
- Death of Laisrén mac Nad Froích (St. Molaise).
;573
- Death of Abbot Brendan of Birr,{{cite web|last=Jones|first=Terry|title=Brendan of Birr|work=Patron Saints Index|url=http://catholicforum.com/saints/saintb57.htm|access-date=2007-12-30|archive-url=https://web.archive.org/web/20080119135159/http://catholicforum.com/saints/saintb57.htm|archive-date=19 January 2008|url-status=dead|df=dmy-all}} one of the Twelve Apostles of Ireland.
;575
- Convention of Druim Ceat, at which agreement is reached between the Uí Néill and the king of Dál Riata maintaining the peace and the balance of power. The poets are said to have been saved from banishment by the intervention of Columba.{{cite book|editor1=Moody, T. W. |editor2=Martin, F. X. |year=1967|title=The Course of Irish History|publisher=Mercier Press|location=Cork|page=60}}
- Bishop Muiredach of Killala meets with Columba in Ballysadare.
;576
- Death of Colmán Már mac Coirpre, King of Leinster.
;577
580s
;584
- The foundation of the University of Tuaim Drecain (Tomregan) by the Synod of Drumceat on Magh Slécht.
;585
- Suibne mac Colmáin becomes King of Uisnech in Mide of the Clann Cholmáin. He is the son of King Colmán Már mac Diarmato (died 557){{cite book|first=Francis J|last=Byrne|title=Irish Kings and High-Kings|url=https://archive.org/details/irishkingshighki00byrn_0|url-access=registration}} and rules Uisnech until his death in 598.The Laud Synchronisms and Book of Leinster give him a reign of 18 years.
;588
- Áed Dub mac Suibni (died c. 588) was an Irish king of the Cruthin of Dál nAraidi (in modern Ulster). He may have been king of the Ulaid.
590s
;590
- Columbanus and twelve companions set sail for France.
;593
- Death of Áed Dibchine mac Senaig King of Leinster from the Uí Máil branch of the Laigin, the first king of this branch to hold the overlordship of Leinster.
;595
- Death of Saint Berach of Termonbarry
;597
;598
- Monastery established in Ferns, County Wexford, dedicated to Bishop Máedóc of Ferns (St. Áedan or Mogue).{{cite book|title=Blue Guide, Ireland|first=Brian|last=Lalor|page=248|isbn=0-7136-6130-5}}
- Suibne mac Colmáin, King of Uisnech in Mide of the Clann Cholmáin, is killed by his uncle Áed Sláine.
;599–600
- Death of St. Cainnech. He was buried at Aghaboe Abbey, which he had founded.{{cite odnb|id=51008|title=Munster, saints of |last=Johnston |first=Elva|year=2008}} His feast day is commemorated on 11 October in the Roman Catholic Church ([http://www.catholic.org/saints/saint.php?saint_id=171 Catholic Online]) and on the 1 August or 14 August in the Eastern Orthodox Church.
600s
;600
- Death of Uatu mac Áedo a king of Connacht from the Uí Briúin branch of the Connachta.