Russian President Vladimir Putin arrived in Rome for a lightning visit including talks with the pope and Italy's government, which has called for an easing of sanctions despite Moscow's ongoing crisis with the West.
Rome's historic centre is on security lockdown for the visit with 50 streets blocked to traffic and Italian media reporting that mobile phone signals could be scrambled.
Mr Putin landed around an hour late at Fiumicino Airport and his convoy drove into Rome and the Vatican City where he met the pope for closed-door talks.
Mr Putin has arrived late for all three of their encounters, the last of which was in 2015 when the pope urged all parties to the conflict in Ukraine to make a "sincere effort" for peace.
Today's meeting comes a day before the pope receives leaders of Ukraine's Greek Catholic Church.
The church leaders and Vatican officials will begin two days of meetings tomorrow to discuss various problems in their country, a former Soviet republic.
Ukraine's religious world was made tense last year when the country's Orthodox Church, which for centuries effectively had been under control of the Russian Orthodox Church, declared its independence and set up a national Church.
Russia opposes the Ukrainian Orthodox Church having autocephalous, or self-governing status, saying the move had more political than religious motives.
Mr Putin has aligned himself closely with the Russian Orthodox Church and has accused the government in Kiev of flagrantly meddling in the life of Orthodoxy in Ukraine.
The meeting between the pope and Mr Putin will be their first since the Pontiff and Russian Orthodox Patriarch Kirill met in 2016, a landmark step in healing the 1,000-year-old rift between the Western and Eastern branches of Christianity.
Mikhail Gorbachev, the last leader of the Soviet Union, and Boris Yeltsin, the first president of post-Soviet Russia, had invited the late Pope John Paul to visit.
But a trip was not possible because of tensions between the Vatican and the Russian Orthodox Church, the largest and most influential in world Orthodoxy, with 165 million of the world's 250 million Orthodox Christians.
Apart from his meeting three years ago with Patriach Kirill, which was the first in history between a Roman Catholic pope and a Russian Orthodox patriarch, Pope Francis has made a number of visits to countries with predominantly Orthodox populations.
The latest were to Romania and to Bulgaria and North Macedonia earlier this year.
From the Vatican, Mr Putin will meet with Italy's prime minister and president and attend a conference on Italian-Russian dialogue at the foreign ministry.
