This article focuses on two claims to religious authority: Mu ammad al-Mustan ir's proclamation as caliph and the canonisation of King Louis IX (r. 1226-1270). Christian royal sainthood and the Islamic Caliphate were very different institutions with different rules. Despite this obvious contrast, the caliphate of al-Mustan ir (r. 1249-1277) and the saintliness of L...