Maria Vittoria Longhitano, who is 35 and married, belongs to the Italian Old Catholic Church, a small congregation that exited Roman Catholicism in the 19th century.
"Catholicism - which means universality - is crippled without women, because one half of the world does not participate in Christ's mission," said Mrs Longhitano, who will celebrate her first mass today in Milan.
Bishop Fritz-Rene Muller of the Union of Utrecht ordained her over the course of a two-hour mass at Rome's Anglican All Saints' Church in front of about a hundred people.
She was not ordained as an Anglican.
The popular and media interest in her ordination demonstrates that "Christian churches and the Roman Catholic Church in Italy have a popular base ready to embrace the female ministry," Longhitano said.
The Vatican fiercely opposes the ordination of women and has welcomed several conservative Anglican priests defecting to Catholicism after the Anglican Church began allowing women to become priests in 1984.
Roman Catholic clergy - priests and bishops - are all male, which the church believes obeys the directives of Jesus Christ, whose 12 apostles were all men.
SIC: SMHAUS