Muirchertach mac Muiredaig [Muirchertach mac Ercae, Mac Ercae] (d. 534), high-king of Ireland, is first mentioned in the annals in 482 under the name Muirchertach mac Ercae. The late Middle Irish account of the wives and mothers of Irish kings (Ban-Shenchus) gives him an obviously legendary mother, Erc, daughter of Lodarn, king of Alba; his wife is said to have been Duasach, daughter of Daui Tengad Umai (d. 502), an early king of the Connachta. From 482 Muirchertach is quite frequently recorded up to 508, when his reign as king of Tara (high-king) is said to have begun. From 508 until 520 he is not mentioned, but from then until his death in 534 there is another cluster of entries. The early sixth-century annals very probably contain some information recorded retrospectively in the late sixth century, when annals began to be written on Iona; such entries, when they can be identified, are in general dependable, although chronological precision cannot be expected. Subsequently, however, these early annals were much expanded, partly in order to incorporate a version of the legend of St Patrick and King Lóegaire, partly to advance particular dynastic interests.
The record of Muirchertach's career has been subject to both these influences. Its length is extremely suspicious, in the first place, and the way it splits into two separate phases does not add credibility. This may all be a consequence of the need felt by the annalists to stretch the careers of the various sons of Níall Noígíallach (Niall of the Nine Hostages) over a period of eighty years, because they were determined to make Patrick's career begin in the year after Palladius was sent to Ireland (431), and they were also determined to make Patrick face Lóegaire mac Néill, ancestor of one of the least successful of the branches of the Uí Néill. Confusion was also aided by the desire of the annalists to obscure the true power of Coirpre mac Néill: thus a victory in 485 ascribed to Coirpre is also attributed to Muirchertach. Finally, there is possible confusion even in his name. Mac Ercae is quite a common first name; the female equivalent, Dar Ercae, was borne by St Mo Ninne of Killevy. Muirchertach is sometimes known as Muirchertach mac Muiredaig, sometimes as Muirchertach mac Ercae (treating mac Ercae as son of Erc, simply giving his maternal descent), sometimes as Mac Ercae; both Muirchertach and Mac Ercae are found in Adomnán's life of Columba.
Muirchertach's sons, including , lie just within the bounds of reliable annalistic evidence; he himself seems to remain just beyond the limits of reliable knowledge, especially in the legend of his threefold death engineered by a seductress from the other world. The full version of this story, Aided Muirchertaig meic Ercae, in which Muirchertach drowns after being pierced by a spear, belongs to the early twelfth century and to the monastery of Dulane in Meath, but it is already foreshadowed in the brief obit in the annals. Even in the most reliable part of his record, in the second phase of entries from 520 until 534, it is evident from the way information is set out that all the annalists had was a tradition of various named battles against opponents in the midlands, in Leinster and in Munster, which they attempted to assign to various years. The surviving impression is of a great war-leader, the founder of the military power undoubtedly possessed by many of his descendants.
T. M. Charles-Edwards
Adomnán's Life of Columba, ed. and trans. A. O. Anderson and M. O. Anderson, rev. edn, rev. M. O. Anderson, OMT (1991) · Aided Muirchertaig meic Ercae, ed. L. Nic Dhonnchadha (1964) · W. Stokes, ed., The annals of Tigernach [8 pts], Revue Celtique, 16 (1895), 374419; 17 (1896), 633, 119263, 337420; 18 (1897), 959, 15097, 267303, 37491; pubd sep. (1993) · Ann. Ulster · G. Murphy, On the dates of two sources used in Thurneysen's Heldensage: 1. Baile Chuind and the date of Cin Dromma Snechtai, Ériu, 16 (1952), 14556, esp. 14551 · M. C. Dobbs, ed. and trans., The Ban-shenchus [3 pts], Revue Celtique, 47 (1930), 283339; 48 (1931), 163234; 49 (1932), 43789 · W. M. Hennessy, ed. and trans., Chronicum Scotorum: a chronicle of Irish affairs, Rolls Series, 46 (1866) · M. A. O'Brien, ed., Corpus genealogiarum Hiberniae (Dublin, 1962) · K. Meyer, ed., The Laud genealogies and tribal histories, Zeitschrift für Celtische Philologie, 8 (191012), 291338 · F. J. Byrne, Irish kings and high-kings (1973)