Three Roman legates break relations between Western and Eastern Christian Churches through the act of placing an invalidly-issued Papal Bull of Excommunication on the altar of Hagia Sophia during Saturday afternoon divine liturgy. Historians frequently describe the event as the start of the East-West Schism.

Pope Innocent IV issues the papal bull ''ad exstirpanda'', which authorizes, but also limits, the torture of heretics in the Medieval Inquisition.

The Grand Union of the Augustinian order formed when Pope Alexander IV issues a papal bull ''Licet ecclesiae catholicae''.

The Augustinian monastic order is constituted at the Lecceto Monastery when Pope Alexander IV issues a papal bull ''Licet ecclesiae catholicae''.

Pope Boniface VIII issues the Papal bull ''Unam sanctam'' (One Faith).

Pope Clement VI issues the Bull ''Unigenitus''.

Papal bull of Pope Clement VI protecting the Jews accused to have caused the Black Death.

Pope Gregory XI issues five papal bulls to denounce the doctrines of English theologian John Wycliffe.

Pope Innocent VIII issues the ''Summis desiderantes'', a papal bull that deputizes Heinrich Kramer and James Sprenger as inquisitors to root out alleged witchcraft in Germany and leads to one of the most oppressive witch hunts in European history.

James IV of Scotland and Margaret Tudor are married according to a Papal Bull by Pope Alexander VI. A Treaty of Everlasting Peace between Scotland and England signed on that occasion results in a peace that lasts ten years.

Pope Leo X issues a papal bull against slavery.

Martin Luther burns his copy of the papal bull ''Exsurge Domine'' outside Wittenberg's Elster Gate.

Pope Leo X excommunicates Martin Luther in the papal bull ''Decet Romanum Pontificem''.