Echmarcach mac Ragnaill (died 1064/1065) was a dominant figure in the eleventh-century Irish Sea region. At his height, he reigned as king over Dublin, the Isles, and perhaps the Rhinns of Galloway. The precise identity of Echmarcach's father, Ragnall, is uncertain. One possibility is that this man was one of two eleventh-century rulers of Waterford. Another possibility is that Echmarcach's father was an early eleventh-century ruler of the Isles. If any of these identifications are correct, Echmarcach may have been a member of the Uí Ímair kindred. Echmarcach first appears on record in about 1031, when he was one of three kings in northern Britain who submitted to Knútr Sveinnsson, ruler of the Anglo-Scandinavian Empire. Echmarcach is recorded to have ruled over Dublin in 1036–1038 and 1046–1052. After losing Dublin for the final time, he appears to have been seated in the Isles on Mann. In 1061, about a decade after his final defeat in Dublin, Echmarcach appears to have been expelled from the Isles, and may have then fallen back into Galloway. Echmarcach appears to have forged an alliance with the powerful Uí Briain. A leading member of this kindred, Donnchad mac Briain, King of Munster, was married to Cacht ingen Ragnaill, a woman who could have been closely related to Echmarcach. Certainly, Echmarcach's daughter, Mór, married one of Donnchad's Uí Briain close kinsmen. Echmarcach's violent career brought him into bitter conflict with a particular branch of the Uí Ímair who had held Dublin periodically from the early eleventh century. This branch was supported by the rising Uí Cheinnselaig, an Irish kindred responsible for Echmarcach's final expulsion from Dublin and apparently Mann as well. In about 1064, having witnessed much of his formerly expansive sea-kingdom fall into the hands of the Uí Cheinnselaig, Echmarcach accompanied Donnchad—a man who was himself deposed—upon a pilgrimage to Rome. Possibly aged about sixty-five at this point in his life, it was here that Echmarcach died, in either 1064 or 1065. In the decades following his demise, the Uí Briain used Echmarcach's descendants as a means to dominate and control Dublin and the Isles. One of his grandsons eventually ruled as king. Uncertain parentage Echmarcach was the son of a man named Ragnall. Whilst Echmarcach bore a Gaelic name, the name of his father is ultimately derived from Old Norse, a fact that serves to exemplify the hybrid nature of the eleventh-century Irish Sea