In another signal of the openness of his papacy, Francis asked to marry 40 people from different social backgrounds who would be a realistic sample of modern couples.
Popes very rarely perform marriages -- the last one was in 2000.
Marriage "is not an easy road, it's sometimes a contentious trip, but that's life", the pope told the couples, both young and old, as their families gathered for the solemn two-hour ceremony.
One of the couples he married was single mother Gabriella and her partner Guido, whose previous marriage was annulled by an ecclesiastical tribunal.
The last time a pope performed a marriage was under the leadership of John Paul II in 2000, and before that in 1994.
It comes three weeks before a major synod of the Catholic Church will discuss the divisive issues of marriage, divorce and conception.
Francis has shown himself more open than his predecessors on the subject of marriage, and has spoken of more realistic attitude to social problems, raising the issue of broken marriages and abandoned women.
Last January he baptised the child of a single mother in the Sistine Chapel along with the daughter of a couple who had not been married in a church.
