The 85-year-old pope is resigning “because of advanced age,” Benedict told the cardinals of the Catholic Church on Monday.
“Strength of mind and body are necessary, strength which in the last few months has deteriorated in me to the extent that I have had to recognize my incapacity to adequately fulfill the ministry entrusted to me,” the pope told the cardinals, according to the Vatican.
The last pope to resign was Gregory XII in 1415. He did so to end a civil war within the church in which more than one man claimed to be pope.
Benedict, the 265th pope, is the sixth German to serve as pope and the first since the 11th century. He became pope in 2005.
He has led church after the third-longest papacy in church history and during a time in which the church is declining in his native Europe but expanding in Africa and Latin America.
Benedict’s time as pope has been marked with a series of scandals and controversies, including hundreds of new allegations of sexual abuse by priests.
CNN’s Chelsea J. Carter and Richard Allen Greene contributed to this report.