In this first comprehensive monograph on St Erik, the author follows the cult of the Swedish royal saint from its obscure beginnings in the twelfth century up to its climax in the time of the Kalmar Union (1397-1523). The focus of the book lies on the interaction of the cult with different groups within medieval Swedish society and these group's attempts to utilize the prestige of the saint to further their political aims. From the middle of the thirteenth century, the cult was particularly connected to the archbishopric of Uppsala and the royal dynasty of Bjalbo. During the fifteenth century the Swedish royal saint symbolized (together with St Olaf of Norway and St Knut of Denmark) the three kingdoms of the Kalmar Union. At the same time, his prestige was successfully employed in the propaganda of King Karl Knutsson (Bonde) and the three Sture-riksforestandare to legitimate their anti-Union politics. In order to gain a broader perspective, the author uses a wide variety of sources. These include a number of texts which contain information about the cult of the saint (legend, miracle collection, offices, sermons, chronicles, charters). In addition, different sorts of depictions showing St Erik on wall paintings, altarpieces, seals, and coins are used in order to give a comprehensive account of the multifaceted veneration of this saint.