Britannica Sources used in this answer

Why did Pope Alexander III excommunicate Frederick I in 1160?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Medieval manuscript miniature showing Frederick I as a crowned crusader holding an orb and scepter, with Henry of Schaftlarn kneeling and presenting a book to him. — Frederick I Frederick I as a Crusader with (right) Henry of Schäftlarn dedicating to him a copy of the *History of the First Crusade* by Robert of St. Remy; miniature from a manuscript in the Vatican Library.

Pope Alexander III excommunicated Emperor Frederick I in 1160 primarily due to a deep-seated conflict over the legitimacy of the papacy and the growing tension between imperial and ecclesiastical authority.12

Following the death of Pope Adrian IV in 1159, a disputed papal election occurred. While the majority of cardinals elected Cardinal Roland as Alexander III, a pro-imperial minority chose Cardinal Octavian, who became the antipope Victor IV. Frederick I, seeking to maintain influence over the papacy and secure his imperial rights in Italy, convened a council in Pavia in 1160. At this council, Frederick formally recognized Victor IV as the rightful pope and rejected Alexander III.34

In response to Frederick’s intervention and his support for the antipope, Alexander III—who sought a papacy independent of imperial control—excommunicated the Emperor. This act intensified the schism, as Alexander III gained recognition from other European powers, including France, England, and the Norman kingdom of Sicily, while Frederick remained committed to his imperial policy.124