The Photian Schism is a four-year (863–867) schism between the episcopal sees of Rome and Constantinople.At issue is the papal claim to jurisdiction in the East, not accusations of heresy.

The schism arises largely as a struggle for ecclesiastical control of the southern Balkans and because of a personality clash between the heads of the two sees, both of whom are elected in the same year (858) and both of whose reigns end in 867, by death in the case of the Pope, by the first of two depositions for the Patriarch.

The Photian Schism thus differs from what occurs in the 11th century, when the pope's authority as a first among equals is challenged on the grounds of having lost that authority through heresy.