Cathal (d. 1010), son of Conchobar and overking of Connacht, belonged, like his earlier namesake Cathal (qv) (d. 925), to the Síl Muiredaig lineage of Uí Briúin Aí. Indeed, repetitive name-patterns in the pedigree of this dynasty have, in the past, prompted understandable suspicions of dittography. Cathal's father, Conchobar (qv) son of Tadc, from whom the later kings of this lineage would take the surname Ua Conchobair, had died as king (973), to be followed briefly by his cousin Cathal son of Tadg, who soon fell in the battle of Ceis Corainn. Cathal son of Conchobar then succeeded. Like his immediate predecessors, he maintained an allegiance to the Uí Néill overkings. His father's sister Derbail (d. 1010) was married to the powerful Cenél nÉogain king Domnall Ua Néill (qv), and was mother of Domnall's son Áed (qv).
Changes in dynastic politics within Uí Néill brought a shift in Cathal's allegiance; his cooperation with the Clann Cholmáin king of Tara, Máel-Sechnaill (qv) son of Domnall, was likely prompted by expediency – perhaps after the latter had plundered Connacht and taken spoils (992, 998). In any event, Cathal helped Máel-Sechnaill to construct a causeway across the Shannon at Áth Luain in 1001. However, by this time, if not earlier, he was making overtures towards the emerging Brian Bórama (qv), his daughter Dubchoblaig becoming Brian's fourth and final wife. Following the example of his great-grandfather Cathal (d. 925), he withdrew to Clonmacnoise, a foundation with which his lineage was closely associated. He died there as a penitent in 1010 and was succeeded in the kingship of Connacht by his son Tadc in Eich Gil Ua Conchobair (qv).