In this first comprehensive monograph on St Erik, the author follows the cult of the Swedish royal saint from its obscure beginnings in the 12th 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 the medieval Swedish society and their attempts to utilise the prestige of the saint to further their political aims. From the middle of the 13th century the cult was particularly connected to the archbishopric of Uppsala and the royal dynasty of Bjälbo. During the 15th century the Swedish royal saint symbolised (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 used in the propaganda of King Karl Knutsson (Bonde) and the three Sture-riksförestandare to legitimate their anti-Union politics. In order to reach a broad perspective the author uses a wide variety of sources. This includes a number 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, altar pieces, seals, and coins are used in order to give a comprehensive account of the multifaceted veneration of this saint.