Sitriuc Cáech (Sigtryggr) (d. 927), grandson of Ímar (Ívarr), king of Dublin and of York, belonged to the Hiberno-Scandinavian dynasty of Uí Ímair. The sobriquet Cáech (one-eyed), accorded to him in Irish sources, suggests some visual impairment; however, he is alternatively known as Sitriuc Gale (the hero). His grandfather Ímar (qv) (d. 873), paramount ruler of the Scandinavians of Ireland, had based his kingship at Dublin. His father is not named in the sources, but is probably to be identified with either Sigfrid son of Ímar or his brother, Sitriuc. Sitriuc Cáech was one of five grandsons of Ímar who feature in the Irish record from the end of the ninth century, and are generally assumed to have been brothers, although their exact relationship to each other is not made explicit. His alleged siblings include Amlaíb (Óláfr) and Ímar, along with Ragnall (qv) and Gofraid. It is recorded that Sitriuc married a sister of Aethelstan (d. 939), king of the English, but he may have been married earlier. The mother of his only recorded son Óláfr, known in Irish sources as Amlaíb Cuarán (qv) (d. 981), is not named.
In the years after his grandfather's death, the Dublin-based kingship was keenly contested between intruders from other Scandinavian dynasties, notably Albann (qv) and Barid (qv), and the sons of Ímar. No sooner had these achieved political supremacy, than bitter feuding erupted; Sigfrid was killed (888) by his own brother, Sigtryggr, who was himself slain in 896 by other kinsmen. That same year, one of Sitriuc's elder brothers (or cousins), Amlaíb, met his death while apparently raiding the Conaille of Co. Louth. When the Dublin settlement was sacked (902) by an Irish alliance led by the Leinster overking, Cerball (qv) son of Muirecán, Sitriuc – presumably still a boy – was among the ruling elite which fled overseas. Following the loss of another brother, Ímar, on an adventure in Pictland (904), the surviving members of the family settled in Cumbria. They regrouped and spent several years building connections with the Danish kingdom of York and with the remnants of the Scandinavian ‘great army’, returned from the Continent.
In 917 Sitriuc, now a young man, led a naval fleet to Ireland in support of Ragnall's expedition, which aimed to control the Scandinavian bases at Waterford and Dublin. He brought his fleet to Cenn Fuait (probably Glynn, near the River Barrow, parish of St Mullins, Co. Carlow). The topographical information in the various annals is confusing, but according to the Annals of Ulster Sitriuc landed in eastern Leinster. He crushed a Leinster army under the Uí Muiredaig king Augaire son of Ailill, while Ragnall defeated the king of Tara, Niall Glúndub (qv), in the south Co. Kilkenny area. Some accounts note that his forces followed up their victory over the Leinstermen at Cenn Fuait with an attack on Kildare.
Sitriuc then took possession of the settlement at Dublin, but at what stage thereafter he laid claim to kingship is not clear. In 918, the year in which Ragnall departed for York, Sitriuc engaged in hostilities with Niall Glúndub, who was clearly anxious to dislodge him from his new powerbase. This contest, which for a time amounted to a standoff, culminated in a major battle, fought at Islandbridge, near Dublin, on 17 December 919, in which Sitriuc defeated and killed the king of Tara, along with several regional kings of Leth Cuinn (the northern half of Ireland). His victory guaranteed the security of the Dublin settlement for decades. In 920, however, while Sitriuc's forces were conducting a raid in Brega, they were attacked by the new Southern Uí Néill king, Donnchad Donn (qv), and suffered heavy losses. This was a serious setback for Sitriuc, and shortly afterwards he left Dublin.
According to the Annals of Ulster, Sitriuc abandoned the settlement ‘through the power of God’ (per potestatem divinam) – which perhaps reveals an Uí Néill perspective – although it seems that his departure preceded a particularly violent attack on Kells by the Norsemen. His brother (or cousin) Gofraid took his place at Dublin. Whether Sitriuc's intention was to support Ragnall, or to challenge him is unclear, but after the latter's untimely death (921) he obtained control of York. Having gained acceptance as king of the Northumbrians, he met with Aethelstan, king of the English, at Tamworth on 30 January 925/6. His marriage to the latter's sister was a gesture designed to seal an agreement between them.
Sitriuc, styled ‘king of the Dubgaill and Finngaill’ (dark and fair foreigners) in the Irish annals, died in 927, immatura etate (at a young age). He was probably in his mid thirties. In the years immediately following his death, Gofraid – from his Dublin base – laid claim to York; on Gofraid's death in 934 his son Amlaíb (qv) (d. 941) succeeded him as king of Dublin. Later, Sitriuc's son Amlaíb Cuarán, having been driven from York, also reigned at Dublin.