Benedict XVI has become the first pope in 600 years to resign, ending an eight-year pontificate shaped by struggles to move the church past sex abuse scandals and to reawaken Christianity in an indifferent world.
The Swiss Guards standing at attention in Castel Gandolfo shut the gates of the palazzo shortly after 8pm local time, symbolically closing the doors on a papacy whose legacy will be most marked by the way it ended - a resignation instead of a death.
In a final farewell to his cardinals as pope, Benedict tried to dispel concerns about the unprecedented future awaiting the Catholic Church, with one reigning and one retired pope living side-by-side.
He pledged his "unconditional reverence and obedience" to his successor.
In a changing of the guard, the Swiss Guards in their yellow-and-blue striped uniforms handed over the responsibility of protecting Benedict to Vatican police as some of the faithful outside shouted "Viva il papa!" - Long live the pope!
The pope's journey into retirement began with an emotional send-off from the Vatican, with Swiss Guards in full regalia and prelates kneeling to kiss Benedict's papal ring one last time.
Benedict's closest aide wept by his side as they took their final walk down the marbled halls of the Apostolic Palace.
As bells tolled in St Peter's and in church towers across Rome, the 85-year-old Benedict flew by helicopter to the papal vacation retreat in Castel Gandolfo in the hills south of Rome where he will spend the first two months of his retirement.
Benedict leaves behind a church in crisis, still coping with the fallout of the sex abuse scandals, a central Vatican administration torn by divisions, and what Benedict said was a crisis of faith, with baptised Catholics in places of ancient Christian tradition thinking they can do without God.
In his final public remarks as pope, Benedict pledged to continue working for the good of the church in his retirement. He told a packed piazza from the palace balcony that, as of his retirement: "I am simply a pilgrim beginning the last leg of his pilgrimage on this Earth."