Pope Benedict pledged his "unconditional reverence and obedience" to his successor Thursday, then left the Vatican as the first Roman Catholic Church leader to resign in 600 years.
Benedict flew from the Vatican by helicopter to the papal residence of Castel Gandolfo near Rome, several hours before his eight-year papacy was to end officially at 8 p.m., local time (1900 UTC).
The 85-year-old pontiff said farewell privately to Roman Catholic cardinals in the Vatican's Clementine Hall, urging them to unite as they prepare to choose the next pope from among their ranks in the coming weeks.
Church officials and workers applauded as Benedict departed. Church officials sealed the papal apartment overlooking St. Peter's Square after he left.
In a final message on his official Twitter account, the leader of the world's one billion Catholics thanked his followers for their "love and support." He also wrote, "May you always experience the joy that comes from putting Christ at the center of your lives."
In the coming days, Roman Catholic cardinals will gather in the Vatican's Sistine Chapel for a conclave, a group meeting bound by centuries-old tradition that will elect a new pope.
Cardinals who are 80 or older will not vote.
On Wednesday, Benedict gave an emotional final audience in St. Peter's Square in Rome. He told thousands of onlookers that despite troubles and "stormy waters" weathered by the church during his tenure, God will not let the institution sink.
He said he was aware of the novelty and the gravity of his decision to step down, but assured the faithful that he had made the move "with profound serenity of spirit." He said he has great trust in the future of the Roman Catholic Church.
Some believers have been disturbed by the Vatican's announcement that in his retirement Benedict will be referred to as "pope emeritus" and continue wearing the white garments he wore while in office. Critics foresee possible tension between Benedict and the new pope who succeeds him, but church authorities insist the transition will be a peaceful one and that Benedict's presence will not cast a shadow over the new leader.
Benedict has said his goal after stepping down is to live quietly in prayer and meditation - in his words "hidden to the world."