Shock, sadness and declarations of faith met Pope Benedict XVI's announcement that he would retire February 28.
Here's a look at reaction from around the world:
In his native land, Chancellor Angela Merkel said she had the "very highest respect" for Benedict's decision to step down - a move the pontiff's brother said he had been considering for months amid ailing health.
"If the pope himself has now, after thorough consideration, come to the conclusion that he no longer has sufficient strength to exercise his office, that earns my very highest respect," Merkel said.
The pontiff's older brother, 89-year-old Georg Ratzinger, told the dpa news agency in Regensburg that his brother had been advised by his doctor not to take any more trans-Atlantic trips and was having increasing difficulty walking.
"His age is weighing on him," Ratzinger said.
In Poland, the homeland of Benedict's predecessor, John Paul II, Archbishop of Warsaw Kazimierz Nycz said Benedict's decision was "wise and brave" and made out of concern for the leadership of the global church.
In Krakow, Cardinal Stanislaw Dziwisz said he was "surprised like everybody else" but said cardinals at the Vatican could see that Benedict was "weakening, had problems walking" even as his intellect remained strong.
Antonio Marto, the bishop of Fatima in central Portugal, said Benedict XVI's resignation presents an opportunity to pick a church leader from a country outside Europe where Catholicism is more vibrant.
"Europe today is going through a period of cultural tiredness, exhaustion, which is reflected in the way Christianity is lived," Marto told reporters. "You don't see that in Africa or Latin America where there is a freshness, an enthusiasm about living the faith.
"Perhaps we need a pope who can look beyond Europe and bring to the entire church a certain vitality that is seen on other continents."
US President Barack Obama is sending his thanks and prayers to Pope Benedict.
Obama says he and first lady Michelle Obama have warm memories of their 2009 visit with the pope. Obama is offering best wishes to the cardinals who will gather in mid-March to choose his successor, and says Catholics play a key role in the US and abroad.
In Cincinnati, Ohio, Archbishop Dennis M Schnurr, who was appointed by Benedict, said Benedict's decision to resign reflected an unselfish attitude.
"In announcing his resignation, Pope Benedict XVI has acted humbly and unselfishly for the good of the church," Schnurr said in a statement. "That same spirit has characterised his entire life of service,"
At St Andrew by the Bay in Annapolis, Maryland, the Reverend Jeffrey Dauses noted that as the world has changed, so have the demands on the papacy.
"It's not the world of the Middle Ages. It's not the world even of in the earlier part of this century when the pope pretty much stayed in Rome, did everything from Rome," Dauses said. "Nowadays with travel, with the expectations of an incredibly high profile, public life, he's not a young man. I mean, he's at an age where in our culture he would be taking it easy and resting, and we're expecting him to keep this grueling schedule as pope, and he simply had the ability to say, 'I can't do that."'
New York Cardinal Timothy Dolan said electing a new pope was all new to him since he's still learning what it means to be archbishop. At a news conference Monday, Dolan quipped he was "still writing thank-you notes from when I was made a cardinal" last year.
The African nation with biggest Christian population, Nigeria, has some 20 million practicing Catholics. In Lagos, Nigeria's largest city, trader Chukwuma Awaegwu put his feelings simply Monday: "If I had my way an African should be the next pope, or someone from Nigeria."
"It's true; they brought the religion to us, but we have come of age," he said. "In America, now we have a black president. So let's just feel the impact of a black pope."
But Cardinal John Olorunfemi Onaiyekan, a Nigerian who was made a cardinal in November by Benedict, said papal politics are not normal politics.
"Popes come and popes go. It doesn't mean when a pope comes the church completely changes, now. It isn't like a politician who wins an election and begins to implement manifestos," Onaiyekan said. "It is a different ball game all together, and I hope people out there realize that."
In Cuba, site of one of Pope Benedict's final trips, the few parishioners outside Havana's Cathedral before doors opened early Monday said they understood his reasons for stepping down and hoped it would open the door to a younger pontiff.
"The church must bring itself up to date with the modern world," said Angel Aguilera, a 33-year-old municipal worker.
But Luz Divina Martinez, a 46-year-old housewife passing the cathedral on her way to market, argued against picking too young a successor, noting the problems the church has had with charges of sexual misconduct by some of its priests.
"A pope of a certain age will be more respected and will better know how to show each person the right way," she said.