World leaders, Catholic officials and mourners from around the globe are at the pope's funeral in Rome.
Among them are US President Donald Trump, Prince William, French President Emmanuel Macron, Spain's King Felipe VI and Queen Letizia, and former US President Joe Biden.
Pope Francis's vocal opinions on global issues occasionally put him at odds with some world leaders.
Dignitaries are sitting on the the right-hand side of the square - facing the Basilica - with the heads of state for Argentina and Italy taking the front seats.
They are followed by reigning sovereigns followed by heads of states who will be seated in alphabetical order by country, in French.
Starmer described Pope Francis's leadership as "courageous" in a statement following his death and said he was a pope "for the poor, the downtrodden and the forgotten".
Prince William is at the funeral on behalf of his father, King Charles III, in keeping with recent tradition. The King, when he was Prince of Wales, attended the funeral of Pope John Paul II in 2005 on behalf of Queen Elizabeth II.
King Charles and Queen Camilla were among the last high-profile figures meet the Pope at his residence Casa Santa Marta during a royal visit to Italy earlier this month.
King Charles said he and Camilla had "heavy hearts" following the Pope's death
The King paid tribute to Pope Francis's "compassion" and said "through his care for both people and planet, he profoundly touched the lives of so many".
He said he and the Queen remembered "with particular affection" their meetings with the Pope over the years, and "were greatly moved to have been able to visit him earlier in the month".
Pope Francis and Lula at the Vatican in 2021
Lula, who shared a personal rapport with the Pope.
Brazil is home to the world's largest Catholic population, with over 100 million Catholics. Following news of Pope Francis's death on Monday, Lula declared seven days of mourning.
"Humanity loses today a voice of respect and welcome for others," Lula said.
Noting the meetings he had held with the Pope over the years, Lula said: "We were able to share our ideals of peace, equality, and justice - ideals that the world has always needed, and will always need."
Trump and Pope Francis photographed during their meeting at the Vatican in 2017
Trump announced on his Truth Social platform that he and first lady Melania would attend the Pope's funeral, marking the first foreign trip of his second term as US president.
After news of the Pope's death emerged, Trump ordered that all federal and state flags be flown at half-mast in honour of the late pontiff. He called Pope Francis "a very good man" who "loved the world" and "he especially loved people that were having a hard time".
The pair clashed in the past. In 2016, Pope Francis criticised Trump's proposal to build a wall on the US-Mexico border, saying a person "who thinks only about building walls" and "not building bridges, is not Christian".
Trump hit back, saying: "For a religious leader to question a person's faith is disgraceful."
After Trump met the Pope during a trip to the Vatican in 2017, he said: "He is something, he's really good. We had a fantastic meeting."
In February, Pope Francis described Trump's mass deportations as a "major crisis".
Marcos Jr described Francis as the "best Pope in my lifetime".
"A man of profound faith and humility, Pope Francis led not only with wisdom but with a heart open to all, especially the poor and the forgotten," he said.
The Philippines is one of the world's most Catholic countries, with almost 80% of Filipinos identifying as Roman Catholic.
Pope Francis's last visit to the country in 2015 drew a crowd of six million people at an outdoor Mass in the capital city Manila, a record for a papal event.
In the running to become the next Pope is Luis Antonio Gokim Tagle, a Cardinal from the Philippines. Cardinal Tagle has been called the "Asian Francis" because of a dedication to social issues and sympathy for migrants.
Pope Francis greets people following his Mass in Manila in 2015
"We grieve together with Catholics and all Christians who looked to Francis for spiritual support," Zelensky said following the Pope's death
The Ukrainian president will travel to Vatican City with first lady Olena Zelenska for the funeral.
There had been uncertainty about whether the Ukranian president would travel to Vatican City, following a strike on Kyiv on Thursday.
In an earlier tribute to Pope Francis, Zelensky said: "He knew how to give hope, ease suffering through prayer, and foster unity."
"He prayed for peace in Ukraine and for Ukrainians."
Following Russia's invasion of Ukraine in 2022, Francis made repeated calls for peace and an end to the war. The two leaders met several times at the Vatican, most recently last October.
Following that meeting, Pope Francis wrote on X: "All nations have the right to exist in peace and security. Their territories must not be attacked, and their sovereignty must be respected and guaranteed through peace and dialogue."
Earlier in 2024, Ukraine had strongly rejected a call by the pontiff for Kyiv to negotiate an end to the war and have "the courage to raise the white flag".
Other political figures and royals who were due to attend the Pope's funeral include: