Goibnenn mac Conaill (flourished 537)all dates per The Chronology of the Irish Annals, Daniel P. McCarthy was the first king of the Ui Fiachrach Aidhne mentioned in the annals. He was the great-grandson of the high king Nath Í (died 445).T.M. Charles-Edwards, Early Christian Ireland, Appendix XXIII
In 537 he defeated the King of Uisnech, Maine mac Cerbaill, of the Southern Ui Neill at the Battle of Claenloch (near Kinelea, Co. Galway) and Maine was slain.Annals of Ulster AU 538.2; Annals of Tigernach 537.1 Maine was attempting to secure the hostages of the Uí Maine. This battle marked the division of the Ui Maine subject to Connacht and the Cenél Maine of Tethba, subject to the Southern Ui Neill.Francis J.Byrne, Irish Kings and High-Kings, pg.92 This victory would lead to the domination of the kingship of Connacht by the Ui Fiachrach Aidne in the 7th century.
Notes
References
Annals of Ulster at CELT: Corpus of Electronic Texts at University College Cork Annals of Tigernach at CELT: Corpus of Electronic Texts at University College Cork Byrne, Francis John (2001), Irish Kings and High-Kings, Dublin: Four Courts Press, Charles-Edwards, T. M. (2000), Early Christian Ireland, Cambridge: Cambridge University Press, Revised edition of McCarthy's synchronisms at Trinity College Dublin.