The Christianization of Scandinavia, as well as other Nordic countries and the Baltic countries, took place between the 8th and the 12th centuries. The realms of Denmark, Norway and Sweden established their own archdioceses, responsible directly to the pope, in 1104, 1154 and 1164, respectively. The conversion to Christianity of the Scandinavian people required more time, since it took additional efforts to establish a network of churches.

Vikings were seafaring people originally from Scandinavia, who from the late 8th to the late 11th centuries raided, pirated, traded, and settled throughout parts of Europe. They also voyaged as far as the Mediterranean, North Africa, the Middle East, Greenland, and Vinland. In their countries of origin, and some of the countries they raided and settled in, this period is popularly known as the Viking Age, and the term "Viking" also commonly includes the inhabitants of the Scandinavian homelands as a whole. The Vikings had a profound impact on the early medieval history of Scandinavia, the British Isles, France, Estonia, and Kievan Rus'.