Arguably the most powerful Munster king before Brian Boru, Cathal belonged to the Eoganacht Glennamnach dynasty. His father, Finguine (d. c. 695) son of Cu-cen-Mathair, is styled king of Munster in his obit, but little is known of his reign. Cathal’s predecessor as overking was Cormac (d. 713) grandson of Maenach, of the Eoganachta of Cashel. The Munster regnal list, in claiming a twenty-nine-year reign for Cathal, implies that he succeeded his predecessor immediately. However, there are indications that he struggled to assert his authority at provincial level. In 715, Murchad son of Bran, the Ui Dunlainge over king of Leinster, marched on Cashel. Further doubt is cast on the extent of Cathal’s sway during these early years by the record of a rival, Eterscel son of Mael-umai of Eoganacht Aine, who is styled king of Cashel in his obit at 721. However, from that time onward, Cathal emerges not only as a strong over king of Munster, but as the dominant political force in Leth Moga, and as a serious threat to the political order that the Ui Neill dynasties strove to establish.
Cathal’s marriage to Caillech (d. 731) daughter of Dunchad Ard, a princeling of Ui Meicc Brocc, possibly reflects an early initiative—even before his accession to kingship—to forge alliances with dynasties to the east of Cashel. In any event, he had a daughter Tualaith, and a son (or, more likely, grandson) Artri. Later, he secured a judicious marriage pact with the Ui Dunlainge dynasty of Leinster, when his daughter Tualaith wed Dunchad son of Murchad. It is not clear whether the marriage in question was arranged before or after 721, but in that year, as is widely noticed in the annals, Cathal joined forces with Murchad to plunder Brega (east Co. Meath and north Co. Dublin). Following this, the (admittedly partisan) Annals of Inisfallen make the dramatic claim that the Ui Neill king of Tara, Fergal son of Mael-duin, submitted to Cathal. An appended text, which reckons Cathal and Brian Boru among five Munster kings who "ruled Ireland," resembles (eleventh- or twelfth-century) Ua Briain propaganda and fuels misgivings about the submission claim.
Yet, it is clear that Cathal overshadowed Leth Moga. Although it was the Ui Dunlainge ruler, Murchad, and his subkings who defeated and slew Fergal mac Maele-duin (722) in the crucial battle of Allen (Co. Kildare), Cathal presumed to intervene as kingmaker in Leinster following Murchad’s death in 727. He supported his son-in-law, Dunchad, against his brother, Faelan. In the ensuing battle at Knockaulin (Co. Kildare), Cathal and his principal ally, the king of Osraige, were discomfited, Dunchad was fatally wounded, and Faelan seized the overkingship of Leinster. It is possible that Faelan’s subsequent marriage to Tualaith was intended as an affront to Cathal (the new Leinster king apparently opposed his designs), in which event her motives might well be questioned. Alternatively, it may have represented an attempt at settling differences. Either way, the years that followed witnessed strenuous efforts by Cathal to assert authority over Leinster. In 732, he was defeated by the king of Uf Chennselaig— but invaded Leinster again three years later. The Annals of Ulster maintain that he was repulsed with heavy losses, including his ally the king of Osraige, but Inisfallen insists that he secured victory over his recalcitrant son-in-law, Faelan.
The case for Cathal, in parallel with his Leinster ventures, having challenged Uf Neill supremacy in Mide has drawn considerable debate. The Annals of Ulster at 733 records battles at the symbolic sites of Tailtiu (Teltown, Co. Meath) and Tlachtga (Hill of Ward, Co. Meath) involving one Cathal. Many (e.g., Binchy, Byrne, Jaski, Swift, Herbert) identify the protagonist as Cathal mac Finguine, but some (O Riain, Charles-Edwards) contest this, instead suggesting Cathal mac Aeda of Sfl nAeda Slaine. Those favoring Cathal mac Finguine note that he had previously invaded Brega; besides, the annal record at 733 contains no patronymic, which might be expected for a less well-known dynast. This annal entry aside, however, there are strong indications that Cathal not only claimed sway beyond Mun-ster but was feared as a threat by the Uf Neill. The poem "Teist Cathail meic Finguine," in the Book of Leinster, styles him Ardri Temrach (high-king of Tara), while the law tract "Bretha Nemed Toisech" (probably a Munster product dating to 721-742) makes reference to the Feis of Tara. Even more significant is the probability that the Uf Neill regnal poem "Baile Chuinn," in mentioning fer fingalach (a kin-slaying man)—a descendant of Corc (an Eoganachta dynast) who is "overlord of Munster of great princes in Tara"—refers to Cathal mac Finguine.
In 737, Cathal attended a rfgdal (royal meeting) at Terryglass (Co. Tipperary) with Aed Allan son of Fergal, the new Uf Neill king of Tara. Presumably, the aim was to conclude a nonaggression pact, but the location of the meeting, bordering Leth Moga and Leth Cuinn, suggests mutual respect, with neither king summoned into the other’s realm to betoken submission. The subsequent extension of the Rule of Patrick throughout Ireland— which recognized the ecclesiastical authority of Armagh in Munster—need not imply capitulation by Cathal, and may even have allowed him greater influence over Munster’s Patrician foundations. However, it seems unlikely that Cathal—unless under duress—would have allowed Aed Allan to intervene in Leth Moga. Acknowledging that the annal record for 738 is somewhat disordered, it is possible to interpret Aed Allan’s invasion of Leinster and defeat of its rulers—which seemingly drew no reaction from Cathal—as itself a response to the latter having taken the hostages of Leinster earlier in the year.
Cathal died in 742. Later assessments of his reign as a "milestone" ensured his place in Middle Irish literature, being featured in the historical tale Cath Almaine (the Battle of Allen) and in the satire Aisling Meic Conglainne as the king from whom the hero Mac Conglainne expels a demon of gluttony. Following his death, the succession record for Munster is confused; apparently, he was followed by ephemeral kings from other Eoganachta lineages. His son—or grandson— Airtn (d. 821) regained the kingship in 796, and was ancestor of later Eoganacht Glennamnach kings.
