The most senior Catholic figures spoke of the 85-year-old Pope's "great courage" in making the announcement that he is to resign as leader of the more than billion-strong global Catholic Church because of his age and infirmity.
The German-born Pope's shock announcement that he is to resign on February 28, the first Pope to do so in nearly 600 years, sets the stage for a papal conclave to elect his replacement by the end of next month with no clear front runner to succeed him.
Elected aged 78 years old in 2005 as the oldest pontiff for a century and a half, the Pope made a four-day state visit to Scotland and England in 2010.
The Most Rev Vincent Nichols, Archbishop of Westminster and leader of Catholics in England and Wales, said the announcement had "shocked and surprised" everyone.
"Yet, on reflection, I am sure that many will recognise it to be a decision of great courage and characteristic clarity of mind and action," he said.
"The Holy Father recognises the challenges facing the Church and that 'strength of mind and body are necessary' for his tasks of governing the Church and proclaiming the Gospel.
"I salute his courage and his decision."
Their tributes were joined by the two most senior clerics in the Church of England, the Most Rev Justin Welby, Archbishop of Canterbury, and Dr John Sentamu, Archbishop of York.
Archbishop Welby said: "It was with a heavy heart but complete understanding that we learned this morning of Pope Benedict's declaration of his decision to lay down the burden of ministry as Bishop of Rome, an office which he has held with great dignity, insight and courage.
"I speak not only for myself, and my predecessors as archbishop, but for Anglicans around the world, in giving thanks to God for a priestly life utterly dedicated, in word and deed, in prayer and in costly service, to following Christ."
Prime Minister David Cameron, who met the Pope in London during his visit to Britain in 2010, said: "He has worked tirelessly to strengthen Britain's relations with the Holy See.
"His visit to Britain in 2010 is remembered with great respect and affection. He will be missed as a spiritual leader to millions."
Labour leader Ed Miliband said Pope Benedict had made a "brave" decision.
"Many people will remember his historic visit to the UK in 2010 – which was a very special moment for many, especially Catholics, across the country," he said.
"His decision to stand down is a brave one and we know he will not have reached it lightly.
"The choice of a successor is clearly an important one for the Catholic Church.
"Our thoughts are with those who must make such a critical decision on behalf of millions around the world."
Up to 120 cardinals, aged under 80 and from all over the world, will vote to choose the successor to Pope Benedict.
Cardinal Murphy-O'Connor, the former Archbishop of Westminster and leader of Catholics in England and Wales, who turned 80 last August, will take part in the discussions by cardinals to elect the Pope's successor, but will not be eligible to cast a vote on grounds of his age.
The Pope announced his decision in Latin during a meeting of Vatican cardinals.
He emphasised that carrying out the duties of being Pope requires "both strength of mind and body".
"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths due to an advanced age are no longer suited to an adequate exercise of the Petrine ministry," he told the cardinals.
"I am well aware that this ministry, due to its essential spiritual nature, must be carried out not only by words and deeds but no less with prayer and suffering.
"However, in today's world, subject to so many rapid changes and shaken by questions of deep relevance for the life of faith, in order to govern the barque of St Peter and proclaim the Gospel, both strength of mind and body are necessary - strengths which in the last few months, has deteriorated in me to the extent that I have had to recognise my incapacity to adequately fulfil the ministry entrusted to me."
The last Pope to resign was Gregory XII in 1415 as part of a deal to end the Great Western schism among competing papal claimants.
Benedict called his choice "a decision of great importance for the life of the church".