Pontiff, 85, who has arthritis, says he will step down on 28 February after nearly eight years as head of Catholic church
Pope Benedict XVI stunned the world and left the Catholic church reeling when he said on Monday that he would resign – the first pope to do so since the middle ages.
The move, announced without warning, will take place on 28 February and leave the papacy vacant until a successor is chosen.
A Vatican spokesman said the pontiff's aides were "incredulous" when he told them he would step down because he was too weak to fulfil his duties. The pope summoned a meeting of cardinals to tell them of "a decision of great importance for the life of the church".
His successor is expected to be elected by the end of March and possibly for the beginning of holy week on 24 March. Pope Benedict will honour public commitments and engagements until the date of his resignation, after which he will move to a summer residence near Rome and then to a former monastery within Vatican territory.
Benedict, who became the 265th pope in 2005, has arthritis, particularly in his knees, hips and ankles. He had been due to travel to Brazil, the largest Catholic country in the world, in July for a youth festival, but concerns had been raised among Vatican observers about whether he was fit enough.