Ailill mac Dúnlainge (died 871)

Who is Ailill mac Dúnlainge (died 871)?

Ailill mac Dúnlainge (died 871) was a King of Leinster of the Uí Muiredaig sept of the Uí Dúnlainge branch of the Laigin. This sept had their royal seat at Maistiu in South Kildare in what is now Ireland. He was the son of Dúnlaing mac Muiredaig, a previous king. He ruled from 869-871.

There is much confusion in the king lists during this period for Leinster. Ailill is the first person awarded the title King of Leinster in the Annals of Ulster at his death notice since 838. Francis John Byrne suggests that the root of this apparent confusion lay in the fact that the Uí Dúnlainge kings exercised little real authority due to the aggressions of their western neighbour Cerball mac Dúnlainge, King of Osraige. Cerball, while unable to install himself as king of Leinster, was able to prevent any rival king exercising real power there.

In 870 the high king Áed Findliath invaded Leinster and overran it from Áth Cliath to Gabrán. Meanwhile his ally Cerball mac Dúnlainge of Osraige invaded Leinster from the west. He reached Dún Bolg where his camp was attacked by the Laigin who were at first successful, but in a counter-attack they were put to flight. Ailill's name is not connected with these events which state that Muiredach mac Brain was the King of Leinster who fought the forces of Cerball. The Fragmentary Annals give a lengthy account of this event and state that Cerball met up with the high king's forces at Belach Gabrán but both forces then retitred and the hostages of the Laigin were not taken.