Pope Benedict XVI, who holds his final general audience in St Peter's Square on Wednesday, will be remembered as a traditionalist who gave up on a papacy overshadowed by infighting within the Roman Catholic Church and a toxic sex abuse scandal.
The 85-year-old German pontiff, who said his age prevented him from carrying on in a fast-changing world, is a soft-spoken intellectual who has appeared overwhelmed by turmoil within the Vatican.
Benedict succeeded the long-reigning and popular John Paul II in April 2005 aged 78 after serving for nearly a quarter-century as the Church's chief doctrinal enforcer, earning himself the nickname "God's Rottweiler".
Cardinal Joseph Ratzinger's conservative outlook, his nationality and age were all seen as handicaps from the start of his papacy.
"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 said in his shock announcement to Vatican prelates in Latin on February 11.
Benedict, the first pope to resign since the Middle Ages, focused his energy on issues dear to his heart, such as the foundations of Christianity and inter-faith relations.
During a trip to the Holy Land in 2009 he called for a two-state solution, and he used a 2012 visit to Lebanon to urge Middle Eastern Christians and Muslims to forge a harmonious, pluralistic society.
The pope also fought to stem growing secularism in the West, and repeatedly stressed family values, fiercely opposing abortion, euthanasia and gay marriage.
In a bid to reach young people he set up a Twitter account in nine languages and called for the Church to be an active presence on social media.
The pope was also an advocate of environmental causes, setting up renewable energy and organic farming at Vatican properties.
He rejected the ordination of women and marriage for priests -- a sensitive issue which came repeatedly to the fore as the priestly sex abuse crisis intensified.
Considered by many to lack the charisma of his predecessor, Benedict committed a series of public relations blunders at the start of his reign that offended Muslims, Jews, gays, native Indians, AIDS activists and scientists.
He angered the Muslim world with a speech in 2006 in which he appeared to endorse the view that Islam is inherently violent, sparking deadly protests in several countries as well as attacks on Christians.
In 2009, the pope offended Jews by inviting a breakaway ultra-conservative Catholic faction back into the fold by conditionally lifting the excommunication of four bishops, including one who denied the scope of the Holocaust.
But he won praise from the world Jewish community for his efforts to restore mutual trust.
On a trip to Africa, the region hardest hit by AIDS, he said condom use could be aggravating the crisis -- though he later became the first pope to suggest the possible use of contraception to avoid spreading the virus.
Ratzinger was born on April 16, 1927, in Marktl am Inn, in the southern German region of Bavaria. The son of a policeman, he entered a seminary in 1939, the same year he was required to join the Hitler Youth movement.
He was ordained priest in 1951 and taught at several universities, notably in Bonn and Regensburg, before coming to Rome to work as an advisor to the Second Vatican Council, hammering out modernisation reforms from 1962 to 1965.
Pope Paul VI named Ratzinger archbishop of Munich in 1977 and made him a cardinal the same year. It was during the 1978 conclave to elect a successor to Paul VI that Ratzinger got to know Karol Wojtyla, the future John Paul II.
Three years later he agreed to head the Vatican's doctrinal congregation -- once known as the Holy Office of the Inquisition -- a post he would hold for 24 years and which gave him ultimate oversight of a number of sex abuse cases.
While some critics have accused him of helping to cover up suspect priests, others said he simply failed to grasp the seriousness of the crimes.
As pope, Benedict was the first pontiff to apologise for the abuse scandal, expressing "deep remorse" and meeting with victims in person.
But critics accused him of failing to bring culprits to justice.
His papacy was also overshadowed by a longstanding money-laundering scandal at the Vatican bank, which exposed infighting among Benedict's closest allies.
The pope promised greater transparency, but the turmoil raised questions over whether Benedict had control over ambitious cardinals jockeying for power.
The cerebral Benedict failed to stamp his authority on the Curia, the Church's secretive and powerful governing body.
He also appeared to have lost control of his household: in 2012, his butler Paolo Gabriele leaked secret papers to the media, an act of betrayal which not only saddened Benedict but revealed further divisions within the Church.
In retirement, the man who once described himself as "just a humble vicar" says he wants to dedicate himself to prayer and his writing.
Apart from three encyclicals, or instructions to the Roman Catholic flock, he wrote around 40 other works including a best-seller, "Jesus of Nazareth".
"I will always be close to all of you and I am sure you will remain close to me even though I will be hidden from the world," he said at an emotional farewell with priests after announcing his resignation.