Former Pope Benedict, who in 2013 became the first pontiff in 600 years to resign, died on Saturday aged 95 in a secluded monastery in the Vatican where he had lived since stepping down, a spokesman for the Holy See said.
The Vatican said his body would lie in state from Monday in St.Peter's Basilica. The Vatican has painstakingly elaborate rituals for what happens after a reigning pope dies but no publicly known ones for a former pope.
"With sorrow I inform you that the Pope Emeritus, Benedict XVI, passed away today at 9:34 in the Mater Ecclesiae Monastery in the Vatican," spokesman Matteo Bruni said in a statement.
Earlier this week, Pope Francis disclosed during his weekly general audience that his predecessor was "very sick", and asked for people to pray for him.
For nearly 25 years, as Cardinal Joseph Ratzinger, Benedict was the powerful head of the Vatican's doctrinal office, then known as the Congregation for the Doctrine of the Faith (CDF).
He was elected pope on April 19, 2005 to succeed the widely popular Pope John Paul II, who reigned for 27 years. Cardinals chose him from among their number seeking continuity and what one called "a safe pair of hands".
The first German pope in 1,000 years, Benedict himself acknowledged that he was a weak administrator, saying he showed a "lack of resolve in governing and decision taking," during his eight-year papacy which was marked by missteps and a leaks scandal.
Child abuse scandals hounded most of his papacy but he is credited with jump-starting the process to discipline or defrock predator priests after a more lax attitude under his predecessor.
After his resignation, conservatives in the Church looked to the former pope as their standard bearer and some ultra-traditionalists even refused to acknowledge Francis as a legitimate pontiff.
They have criticised Francis for his more welcoming approach to members of the LGBTQ+ community and to Catholics who divorced and remarried outside the Church, saying both were undermining traditional values.