By attributing the term “charismatic” to Saint Louis, Jacques Le Goff identified two sources of charisma: sacred kingship and personal holiness. Without denying these aspects of the holy king’s reputation, we should investigate the nature of the charismatic relationship that linked Louis IX to his contemporaries. The sacrality of Louis IX pre-existed him; his sanctity is a post-death construction. What are the attributes of the living character that would allow us to recognize a charismatic personality? This paper argues that the religious aura of the king, which best echoes the Paulinian version of charisma, was sometimes at odds with the political expectations levied on a medieval ruler, which a Weberian definition of charisma helps to define. In this light, the crusades provided a unique setting where the king’s Christ-like qualities and his political leadership could be reconciled. To conduct this argument, this paper proposes to look for the symptoms of Louis IX’s living charisma in the reactions of his contemporaries, based on the re-examination of classical sources on the life of the king, carefully contextualized.