9th century in Ireland

=800s=

;802
*Death of Muiredach mac Domnaill , King of Mide. He issucceeded by Diarmait mac Donnchado.

;803
*Death of Diarmait mac Donnchado , King of Mide. He is succeeded by Conchobar mac Donnchada.

;804
*Aed Oirnide of the Uí Néill is ordained overking of the Uí Néill by the abbot of Armagh"The Oxford Illustrated History of Ireland." Foster, RF. Oxford University Press, Oxford. 1989] .

;806
*Viking raid on Iona Abbey in which 68 people, the entire population of the abbey, were massacred.

;807
*Construction of the monastery of Kells is begun.
*The Book of Armagh is compiled"Illustrated Dictionary of Irish History." Mac Annaidh, S (ed). Gill and Macmillan, Dublin. 2001]

810s

;819
*Conchobar mac Donnchada or Conchobar mac Donnchado was High King of Ireland with opposition ("rí Érenn co fressabra")

820s

;820
*Feidlimid mac Cremthanin begins his reign as King of Munster, reigning until his death in 847"The Concise History of Ireland." Duffy, S. Gill & Macmillan, Dublin. 2005]

830s

;832
*A Viking fleet of about 120 ships under Turgesius invaded kingdoms on Ireland’s northern and eastern coasts. [http://www.nalanda.nitc.ac.in/resources/english/etext-project/history/ireland/book-2chapter2.html "A Popular History of Ireland", By Thomas D'Arcy McGee]

;833
*Death of Conchobar mac Donnchada, King of Mide and High King of Ireland with opposition [T. W. Moody, Martin, and Byrne, (eds.), "Maps, Genealogies, Lists", p. 192, p. 193, n. 26.]

;836
*Viking raids penetrate deep inland

;837
*Large Viking fleets appear on the River Boyne and the River Liffey, made up of sixty ships at each location.cite book | last=Moody, TW & Martin, FX (eds)| year=1967 |title=The Course of Irish History | publisher=The Mercier Press | location=Cork, Ireland | pages=p 95]

;838 - 841
*A small Viking fleet entered the River Liffey in eastern Ireland, probably led by the chieftain Saxolb (Soxulfr) who was killed later that year. The Vikings overwinter on Lough Neagh in 840 and set up a base, which the Irish called longphorts. This longphort would eventually become Dublin.

;839
*Thorgest (in Latin "Turgesius") was the first Viking to attempt an Irish kingdom. He sailed up the Shannon and the River Bann to Armagh in 839 where he forged a realm spanning Ulster, Connacht and Meath.

840s

;841
*First Longphort built at Linn Duachaill (now Annagassan) on the County Louth coast and at the hurdle ford of the River Liffey.
*Abbot of Armagh driven out by Turgesius, Viking leader.

;842
*First reported Viking-Irish alliance
*Mael Sechnaill I becomes High King of Ireland

;843
*Death of Mael Ruanaid mac Dunnchado, King of Mide since 833.

;845
*Forannan, abbot of Armagh, is captured by the Vikings
*Viking leader Turgesius captured and killed by Mael Sechnaill I, King of Mide.

;846
*Mael Sechnaill I becomes Overking of the Uí Néill, reigning until his death in 862

;847
*Death of Feidlimid mac Cremthanin, King of Munster, who had reigned since 820

;847 or 848
*Birth of Flann Sinna (d. 916), son of Mael Sechnaill I of Clann Cholmáin, a branch of the southern Uí Néill. He was King of Mide from 877.

;848
* Death of Fínsnechta mac Tommaltaig, King of Connacht.
* Viking army defeated by Mael Sechnaill I, High King of Ireland, near modern Skreen, County Sligo
* Viking army defeated by the King of Lagore, Tigernach mac Fócartai, somewhere in modern County Sligo
* Viking army defeated by Ólchobar mac Cináeda, King of Munster, and Lorcán mac Celláig, King of Leinster, near modern Castledermot, County Kildare. The Viking leader Tomrair was killed; he is called jarl and deputy of the king of Lochlann.
* Viking army defeated near Cashel by Ólchobar mac Cináeda.
* Vikings at Cork; besieged by Ólchobar mac Cináeda.
* The "Annales Bertiniani" report the arrival of Irish envoys at the court of Frankish Emperor Charles the Bald. They brought gifts from the "king of the Irish" and announced an Irish victory over Vikings. The Irish annals record several defeats for Viking armies, which of these is meant is unclear. The identity of the "king of the Irish" is no more certain, but Ólchobar mac Cináeda may be intended rather than Mael Sechnaill I.
* Sedulius Scottus arrives at Liège, perhaps having been a member of the embassy to Charles the Bald.

850s

;851
*Máel Sechnaill mac Máele Ruanaid secured the submission of the King of Ulaid. [cite book | last=Moody, TW & Martin, FX (eds)| year=1967 |title=The Course of Irish History | publisher=The Mercier Press | location=Cork, Ireland | pages=p 59]
* Cináed mac Conaing was drowned on the orders of Máel Sechnaill and Tigernach mac Fócartai. [Byrne, Francis John, "Irish Kings and High Kings", p.263.]

;853
* The "Annals of Ulster" report that Amlaíb, "son of the king of Laithlind" arrived in Ireland and collected tribute from the Vikings and the Irish.

860s

;860 or 862
*Death of Mael Sechnaill I, Overking of the Uí Néill, who had reigned since 846.

;864
*Death of Lorcan mac Cathail, King of Mide since 862.

;866
*Aed Finliath clears the northern coastline of Viking bases. He defeated the Vikings at Lough Foyle. [cite book | last=Lalor | first=Brian (ed) | year=2003 |title=The Encyclopaedia of Ireland | publisher=Gill & Macmillan | location=Dublin, Ireland | isbn=0-7171-3000-2 | pages=p 9]

870s

;876
*Flann Sinna becomes King of Ireland

;877
* Flann Sinna mac Maíl Sechnaill becomes King of Mide

880s

;880
*Death of philosopher and poet Johannes Scotus Eriugena

890s

;896
*Death of Flann mac Lonáin, poet
*Death of Sitriuc mac Ímair (Sigtryggr), Viking king (perhaps king of Dublin)

Notes