6th century in Ireland
- 23 March - Death of Bishop Mac Cairthinn of Clogher.
- 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).
- 29 June - A solar eclipse is recorded.
- 2 November - Death of Bishop Erc of Slane (according to some sources; see 513 below).
- 2 November - Death of Bishop Erc of Slane (according to some sources; see 512 above).
- Birth of Abbot Cainnech of Aghaboe at Glengiven near Dungiven in Ulster (according to some sources; see 516 below).
- 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.
- Birth of Abbot Cainnech of Aghaboe at Glengiven near Dungiven in Ulster (according to some sources; see 515 above).
- 6 July - Death of St. Moninne (Darercae) at the convent she established at Killeavy (year varies according to sources).
- Monastery founded in Ballyleague by St. Faithleach of Clontuskert (brother of Brendan).
- 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).
- 7 December - Birth of Columba (Colm Cille or Columcille) in Gartan, missionary monk (died 597).
- 7 December - Death of St. Búite of Monasterboice.
- Death of Eochaid mac Óengusa, an Eoganachta king of Munster. His son Crimthann Srem mac Echado succeeds him.
- St. Ninnidh made the island of Inishmacsaint (island of plain Sorrell) in Lough Erne his headquarters around 523.
- 1 February - Death of St. Brigit of Kildare (year varies according to sources) (born c.451).
- Death of Illan mac Dúnlainge, King of Leinster.
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 534 or 542).
- 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.
- Approximate date - Death of St. Enda of Aran.
- 531 (or 537)
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 527, 528 or 542).
- 20 August - Death of St. Mochta of Louth (disciple of St. Patrick) (in 537 according to some sources).
- Extreme weather events: Famine recorded in Ireland.
- Birth of Columbanus at Nobber in the Kingdom of Meath.
- Approximate date - The Paschal controversy begins in Ireland.
- 12 September or 30 December - Death of Bishop Ailbe of Emly (year varies according to sources; also given as 527, 528 or 534).
- Columba founds Derry.
- Approximate date - Death of Abbot Ciarán of Clonmacnoise (of yellow fever) (according to some sources - see 556 below).
- Roman Catholic Diocese of Ossory, which still exists, founded.
- Death of St. Finnian of Clonard, who founded Clonard Abbey.
- Death of Abbot Ciarán of Clonmacnoise (of yellow fever) (according to some sources - see 546 above).
- Death of the probably legendary Colmán Már mac Diarmato, a king of Uisnech in Mide of the Clann Cholmáin.
- Columba founds a monastery on Iona off the coast of Scotland.
- Brendan founds a monastery at Clonfert.
- Death of Laisrén mac Nad Froích (St. Molaise).
- 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.
- Bishop Muiredach of Killala meets with Columba in Ballysadare.
- Death of Colmán Már mac Coirpre, King of Leinster.
- Death of Brendan.
- Death of Coirpre Cromm mac Crimthainn, King of Munster from the Glendamnach sept of the Eoganachta. He is succeeded by Fergus Scandal mac Crimthainn.
- The foundation of the University of Tuaim Drecain (Tomregan) by the Synod of Drumceat on Magh Slécht.
- 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) and rules Uisnech until his death in 598.
- 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.
- Columbanus and twelve companions set sail for France.
- 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.
- Death of Saint Berach of Termonbarry
- Monastery established in Ferns, County Wexford, dedicated to Bishop Máedóc of Ferns (St. Áedan or Mogue).
- Suibne mac Colmáin, King of Uisnech in Mide of the Clann Cholmáin, is killed by his uncle Áed Sláine.
- Moody, T. W.; Martin, F. X.; Byrne, F. J., eds. (1989). A New History of Ireland. 8: A Chronology of Irish History. A Companion to Irish History, part I. Oxford University Press. ISBN 978-0-19-821744-2.
- List of Published Texts at CELT — University College Cork's Corpus of Electronic Texts project has the full list of Irish Annals.
- Gratton-Flood, W. H. (1907), "The Twelve Apostles of Erin", The Catholic Encyclopedia, New York: Robert Appleton Company, I, retrieved 2008-02-09
- "Annals of Cloontuskert Parish". Retrieved 2013-02-01.
- Annals of Tigernach.
- Mac Annaidh, Séamas, ed. (2001). Illustrated Dictionary of Irish History. Dublin: Gill and Macmillan. ISBN 0717135365.
- McCarthy, Daniel P. (1998). The Chronology of the Irish Annals. Proceedings of the Royal Irish Academy, Section C, Archaeology, Celtic studies, history, linguistics, and literature, 98(6). Dublin: Royal Irish Academy.
- Duffy, Seán (2005). The Concise History of Ireland. Dublin: Gill & Macmillan. ISBN 9780717138104.
- Jones, Terry. "Brendan of Birr". Patron Saints Index. Archived from the original on 19 January 2008. Retrieved 2007-12-30.
- Moody, T. W.; Martin, F. X., eds. (1967). The Course of Irish History. Cork: Mercier Press. p. 60.
- Byrne, Francis J. Irish Kings and High-Kings.
- The Laud Synchronisms and Book of Leinster give him a reign of 18 years.
- Lalor, Brian. Blue Guide, Ireland. p. 248. ISBN 0-7136-6130-5.
- His feast day is commemorated on 11 October in the Roman Catholic Church (Catholic Online) and on the 1 August or 14 August in the Eastern Orthodox Church.