In 1053, the archdiocese of Hamburg-Bremen became patriarchate of the North as part of a process of centralization with which the Curia sought control over Scandinavia and the North Atlantic. Although these ambitions risked being cut short by the German archbishops, who aspired to larger margins of independence, Gregory VII (1073–85) was able to secure the Icelandic diocese of Skálholt as a supporter of Roman reforming ideals. Bishop Gizurr Ísleifsson (1082–1118) maintained direct contacts with the Curia and organized the Icelandic church as a loyal Gregorian agent. In the absence of royal and archepiscopal authority in Iceland, Gizurr was considered ‘king and bishop over the country’: arguably, the pontiff of his own diocese. Through the analysis of Latin and Norse sources, this article explores how Gregorian ideals reached Iceland during the Investiture Controversy and how papal supremacy was built into the foundations of the northernmost diocese of Christendom.