On January 3, 1521, Martin Luther was excommunicated by Pope Leo X from the Roman Catholic Church. From the article:
"Luther excommunicated by Catholic Church
On January 3, 1521, Pope Leo X issued the papal bull Decet Romanum pontificem (“It pleases the Roman Pontiff”), which excommunicated Martin Luther, a German theologian and monk who had been causing the Roman Catholic Church no end of trouble since 1517. With that, the Pope cast Luther out of the Catholic Church—and thereby helped spur the development of the Lutheran church and the Protestant Reformation.
The trouble had begun back on October 31, 1517, when Luther sent his 95 Theses, protesting several Church practices and doctrines, to the Archbishop of Mainz and Magdeburg. By the next summer, Church authorities began to call Luther’s views heretical, though it took three years before Leo X moved formally against him. On June 15, 1520, he issued the bull Exsurge Domine (“Arise Oh Lord”) stating that 41 sentences in Luther’s 95 Theses were heresy.
The Pope gave Luther 60 days to recant these words and another 60 to inform the papacy of his cooperation. If not, the bull said, Luther would be excommunicated.
Luther at first thought the bull might be a trick created by enemies. Once he became convinced the document was indeed from the pope, he attacked it. In November, he published a treatise titled Assertion of All the Articles Wrongly Condemned in the Papal Bull, in which he defended his views—and called the Pope the Antichrist. Meanwhile, Luther’s own works were being burned by supporters of the Pope.
On December 10, sixty days after he had received the bull, Luther summoned his supporters to a gathering in Wittenberg, Germany, and had them build a bonfire. Into it they cast books of canon, or Church, law and Church-supported theological writings. To punctuate his defiance, Luther added a copy of Exsurge Domine to the fire. That response prompted Leo to carry out his threat and issue the excommunication."