Who will be the next pope? The decision could have a profound impact on the Catholic Church and the world's 1.4 billion baptised Roman Catholics.
It also promises to be a highly unpredictable and open process for a host of reasons.
The College of Cardinals will meet in conclave in the Sistine Chapel to debate and then vote for their preferred candidates until a single name prevails.
With 80% of the cardinals appointed by Pope Francis himself, they are not only electing a pope for the first time, but will offer a broad global perspective.
For the first time in history, fewer than half of those given a vote will be European.
And although the college may be dominated by his appointments, they were not exclusively "progressive" or "traditionalist".
For those reasons, it is harder than ever to predict who will be elected the next pope.
Could the cardinals elect an African or an Asian pope, or might they favour one of the old hands of the Vatican administration?
Here are some of the names being mentioned as Francis's potential successor.
Nationality: Italian
Age: 70
Softly spoken Italian Cardinal Parolin was the Vatican's secretary of state under Pope Francis – making him the pope's chief adviser. The secretary of state also heads the Roman Curia, the Church's central administration.
Having acted effectively as deputy pope, he could be considered a frontrunner.
He is viewed by some as more likely to prioritise diplomacy and a global outlook than the purity of Catholic dogma. His critics consider that a problem, while his supporters see a strength.
But he has been critical of the legalisation of same-sex marriage around the world, calling a landmark 2015 vote in favour in the Republic of Ireland "a defeat for humanity".
The bookmakers may back him but Cardinal Parolin will be well aware of an old Italian saying that stresses the uncertainty of the pope-picking process: "He who enters a conclave as a pope, leaves it as a cardinal."
Some 213 of the previous 266 popes have been Italian and even though there has not been an Italian pope in 40 years, the pivot of the upper echelons of the Church away from Italy and Europe may mean there may not be another for now.
Nationality: Filipino
Age: 67
Could the next pope come from Asia?
Cardinal Tagle has decades of pastoral experience – meaning he has been an active Church leader among the people as opposed to a diplomat for the Vatican or cloistered expert on Church law.
The Church is massively influential in the Philippines, where about 80% of the population is Catholic. The country currently has a record five members of the College of Cardinals – which could make for a significant lobbying faction if they all back Cardinal Tagle.
He is considered a moderate within the Catholic definition, and has been dubbed the "Asian Francis" because of a dedication to social issues and sympathy for migrants that he shared with the late pope.
He has opposed abortion rights, calling them "a form of murder" – a position in line with the Church's broader stance that life begins at conception. He has also spoken against euthanasia.
But in 2015 when he was Archbishop of Manila, Cardinal Tagle called for the Church to reassess its "severe" stance towards gay people, divorcees and single mothers, saying past harshness had done lasting harm and left people feeling "branded", and that each individual deserved compassion and respect.
The cardinal was considered a candidate to be pope as far back as the 2013 conclave in which Francis was elected.
Asked a decade ago how he viewed suggestions he could be next, he replied: "I treat it like a joke! It's funny."
Nationality: Congolese
Age: 65
It's very possible the next pope could be from Africa, where the Catholic Church continues to add millions of members. Cardinal Ambongo is a leading candidate, hailing from the Democratic Republic of Congo (DRC).
He has been Archbishop of Kinshasa for seven years, and was appointed cardinal by Pope Francis.
He is a cultural conservative, opposing blessings for same-sex marriage, stating that "unions of persons of the same sex are considered contradictory to cultural norms and intrinsically evil".
Though Christianity is the majority religion in the DRC, Christians there have faced death and persecution at the hands of jihadist group Islamic State and associated rebels. Against that backdrop, Cardinal Ambongo is viewed as a fierce advocate for the Church.
But in a 2020 interview, he spoke in favour of religious plurality, saying: "Let Protestants be Protestants and Muslims be Muslims. We are going to work with them. But everyone has to keep their own identity."
Such comments could lead some cardinals to wonder if he fully embraces their sense of mission - in which Catholics hope to spread the Church's word throughout the world.
Nationality: Ghanaian
Age: 76
If chosen by his peers, the influential Cardinal Turkson would likewise have the distinction of being the first African pope for 1,500 years.
Like Cardinal Ambongo, he has claimed not to want the job. "I'm not sure whether anyone does aspire to become a pope," he told the BBC in 2013.
Asked if Africa had a good case to provide the next pope based on the Church's growth on the continent, he said he felt the pope shouldn't be chosen based on statistics, because "those types of considerations tend to muddy the waters".
He was the first Ghanaian to be made a cardinal, back in 2003 under Pope John Paul II.
Like Cardinal Tagle, Cardinal Turkson was considered a potential pope a decade later, when Francis was chosen. In fact, bookmakers made him the favourite ahead of voting.
A guitarist who once played in a funk band, Cardinal Turkson is known for his energetic presence.
Like many cardinals from Africa, he leans conservative. However, he has opposed the criminalisation of gay relationships in African countries including his native Ghana.
In a BBC interview in 2023, while Ghana's parliament was discussing a bill imposing harsh penalties on LGBTQ+ people, Turkson said he felt homosexuality should not be treated as an offence.
In 2012, he was accused of making fear-mongering predictions over the spread of Islam in Europe at a Vatican conference of bishops, for which he later apologised.
Nationality: Hungarian
Age: 72
A cardinal since the age of 51, Peter Erdo is highly regarded in the Church in Europe, having twice led the Council of European Bishops' Conferences from 2006 to 2016.
He is well known among African cardinals and he has worked on Catholic relations with the Orthodox Church.
The archbishop of Budapest and primate of Hungary grew up in a Catholic family under communism, and he is considered a potential compromise candidate.
Erdo played a prominent role in Pope Francis's two visits to Hungary in 2021 and 2023, and he was part of the conclaves that elected Francis and his predecessor Pope Benedict.
His conservative views on the family have found favour with some parts of the Church and he has navigated the "illiberal democracy" of Hungarian Prime Minister Viktor Orban. During Europe's migrant crisis in 2015, he said the Church would not take in migrants as it was tantamount to human trafficking.
Nationality: Italian
Age: 83
Only cardinals under 80 can vote in the conclave, but Angelo Scola could still be elected.
The former Archbishop of Milan was a frontrunner in 2013 when Francis was chosen, but he is thought to have fallen victim to the adage of entering the conclave as Pope and leaving as cardinal.
His name has resurfaced ahead of the conclave, because of a book he is publishing this week on old age. The book features a preface written by Pope Francis shortly before he was admitted to hospital in which he said "death is not the end of everything, but the beginning of something".
Francis's words show genuine affection for Scola, but the college of cardinals might not see his focus on old age as ideal for a new pope.
Nationality: German
Age: 71
Germany's top Catholic cleric is also very much a Vatican insider too.
The Archbishop of Munich and Freising was chosen as an adviser when Francis became pope in 2013. For 10 years he advised the Pope on Church reform and still oversees financial reform of the Vatican.
He has advocated a more accommodating approach towards homosexuals or transgender people in Catholic teaching.
But in 2021 he offered to resign over serious mistakes in tackling child sexual abuse in Germany's Catholic Church. That resignation was rejected by Francis.
Two years ago he left the Council of Cardinals, the Pope's most important advisory body, in what was seen in Germany as a setback for his career in the Church.
Nationality: Canadian
Age: 80
Cardinal Ouellet has twice before been seen as a potential candidate for Pope, in 2005 and 2013.
For years he ran the Vatican's Dicastery for Bishops, which chooses candidates for the episcopate around the world, so he has played a significant and formative role in vetting the future members of the Catholic hierarchy.
As another octogenarian, he will not be able to play a part in the conclave itself, which may hinder his chances.
Ouellet is viewed as a conservative with a modern outlook, who is strongly in favour of maintaining the principle of celibacy for priests.
He opposes the ordination of women priests, but he has called for a greater role for women in running the Catholic Church, saying that "Christ is male, the Church is feminine".
Nationality: American
Age: 69
Could the papacy go to an American for the first time?
Chicago-born Cardinal Prevost is certainly seen as having many of the necessary qualities for the role.
Two years ago Pope Francis chose Prevost to replace Marc Ouellet as prefect of the Vatican's Dicastery for Bishops, handing him the task of selecting the next generation of bishops.
He worked for many years as a missionary in Peru before being made an archbishop there.
Prevost is not just considered an American, but as someone who headed the Pontifical Commission for Latin America.
He is seen a reformer, but at 69 might be viewed as too young for the papacy. His period as archbishop in Peru was also clouded by allegations of covering up sexual abuse claims, which were denied by his diocese.
Nationality: Guinean
Age: 79
Well-liked by conservatives in the Church, Cardinal Sarah is known for his adherence to doctrine and traditional liturgy and was often considered opposed to Pope Francis's reformist leanings.
The son of a fruit-picker, Sarah became the youngest archbishop aged 34 when Pope John Paul II appointed him prelate in Conakry in Guinea.
He has had a long and impressive career, retiring in 2021 as head of the Vatican's office that oversees the Catholic Church's liturgical rites.
While not considered a favourite for the papacy, he could attract strong support from conservative cardinals.
Nationality: Canadian
Age: 78
Cardinal Czerny was appointed cardinal by Pope Francis and is like him a Jesuit, a leading order of the Catholic Church known for its charitable and missionary work around the world.
Although he was born in the former Czechoslovakia, his family moved to Canada when he was two.
He has worked widely in Latin America and in Africa, where he founded the African Jesuit Aids Network and taught in Kenya.
Czerny is popular with progressives in the Church and was considered close to Pope Francis. He is currently head of the Vatican's Dicastery for Promoting Human Integral Development.
Although a strong candidate, it seems unlikely the cardinals would choose a second Jesuit pope in succession.