(Sigytryggr Silkiskeggi), son of Amlaib (Olafr) Cuaran, was king of Dublin for a period of almost fifty years between 989 and 1036 During this period, the great growth in trade and economic prosperity that had begun under the reign of his father continued to flourish, and the first coinage to be minted in Ireland appeared in Dublin around 997, with the inscription SIHTRIC REX DYFLIN and variants thereof.
Several short interruptions punctuated the long reign of this Hiberno-Scandinavian king. In the early 990s, an ongoing rivalry between the descendants of Amlaib Cuaran and those of Imar (Ivarr) of Waterford was manifested in a struggle for control of Dublin. Sitriuc managed to expel Imar and three ships of Imar’s men from Dublin in 993, but was himself expelled in 994, the kingship going to Ragnall mac Imair. Upon Ragnall’s death in 995, Sitriuc returned to power, only to be expelled again in 999 by Brian Boru. Sitriuc’s expulsion followed Brian’s successful siege of Dublin in the aftermath of the Battle of Glenn Mama; however, after submitting to Brian and giving him hostages, Sitriuc was allowed to return to his kingdom the subsequent year. Sitriuc’s third departure—a pilgrimage to Rome in 1028—was voluntary. During this third absence, Sitriuc’s son Amlaib (Olafr) appears to have become king of Dublin, ceding authority back to his father at some point before 1031. Sitriuc’s pilgrimage is a reflection of the Christian devotion characteristic of his family since the conversion of his father, the most marked legacy of which was Sitriuc’s founding of Christ Church cathedral (c. 1030).
The family’s conversion to Christianity no doubt helped to further facilitate the marital alliances that had been taking place between Norse and Irish dynasties since the mid-ninth century. Not only was Sitriuc himself the product of such a union—his mother was Gormfhlaith, daughter of the Ui Faelain king of Leinster Murchad mac Finn—but he was also a partner in one through his marriage to Slaine, daughter of Brian Boru. Sitriuc’s sister Mael Muire, meanwhile, was married to the king of Tara Mael Sechnaill II, whereas another sister, Ragnall (Ragnhildr), was the wife of Domnall mac Congalaig, king of Brega. The potential benefit of such marriage alliances is seen to best effect in the case of the mutual support afforded between Sitriuc and his mother’s brother, Mael Morda, king of Leinster from 1003 to 1014. It was Mael Morda who killed Ragnall mac Imair in 994, thereby enabling Sitriuc’s return to power, whereas Sitriuc returned the favor in 995 by helping his uncle seize the current king of Leinster, Donnchad mac Domnaill of the Ui Dunchada, thus clearing the way for Mael Morda’s accession. Thereafter, the two supported each other consistently, most notably in their unsuccessful stands against Mael Sechnaill II and Brian Boru at Glenn Mama in 999, and against Brian in the battle of Clontarf in 1014. Clearly, Sitriuc’s bonds to Mael Sechnaill and Brian by marriage were in no way as effective as his bonds by blood to the Ui Faelain.
While Sitriuc’s relations with Mael Sechnaill were generally strained across the board, those with Brian were more mixed. After Brian reinstated Sitriuc following the events of 999, the Dublin king, in conjunction with the Leinstermen, regularly accompanied Brian on his hostings throughout the country. In 1013, however, this cozy relationship changed when Sitriuc joined with Mael Morda against Brian in the hostilities that eventually led to Clontarf. According to contemporary sources, Sitriuc and the Leinstermen were assisted at Clontarf by contingents of Scandinavians from the Orkneys and Hebrides; in later sources this alliance becomes exaggerated to include representatives from almost every corner of the Viking world. The later sources also relate that Sitriuc stayed inside the battlements of the city throughout the conflict, defending his fortress from within, while his Scandinavian allies fought alongside the Leinstermen from without. Given that Sitriuc survived to rule Dublin for more than twenty more years after the battle, despite huge casualties on the parts of his Leinster and Scandinavian allies as well as of Brian’s forces, this account of his whereabouts may indeed reflect the truth.
Ultimately, it was Sitriuc’s fellow Hiberno-Scandinavians rather than any Irish ruler who put an end to his reign as king of Dublin. In 1035, Sitriuc murdered Ragnall Ua Imair, king of Waterford, enflaming the feud with the descendants of Imar. The following year, one such descendant, Echmarcach mac Ragnaill, took over control as king of Dublin and Sitriuc went into exile "across the sea," possibly Wales, and died in 1042.
