Women campaigning for change have come to Rome to make their case, from Europe and the United States but also South Africa, Australia, Colombia and India.
They have different backgrounds and diverse goals -- not all want female priests, with some aiming first for women to become deacons, who can celebrate baptisms, marriages and funerals, although not masses.
But they are united in their frustration at seeing women excluded from key roles in what many view as a "patriarchal and macho" Church.
"The majority of people who support parish life and transmit the faith in families are women, mothers," said Carmen Chaumet from French campaign group "Comite de la Jupe", or the Committee of the Skirt.
"It is paradoxical and unfair not to give them their legitimate place."
"If you go to the Vatican, to a mass, you see hundreds of men priests dressed the same way, and no women," added Teresa Casillas, a member of Spanish association "Revuelta de Mujeres en la Iglesia", "The Women's Revolt in the Church".
"I feel that men are the owners of God."
- 'Voting rights' -
The Synod assembly, which runs until October 29, nevertheless marks a historic turning point in the Church, with nuns and laywomen allowed to take part for the first time.
Some 54 women -- around 15 percent of the total of 365 assembly members -- will be able to vote on proposals that will be sent to Pope Francis.
Vatican observers have called it a revolution. "A first step," say campaigners.
Adeline Fermanian, co-president of the Committee of Skirt, said the pope had given "openings" on the question of ordaining women.
"He recognized that the questions has not been examined sufficiently on a theological level," she said.
Since his election in 2013, Francis has sought to forge a more open Church, more welcoming to LGBTQ faithful and divorcees, and encouraging inter-faith dialogue.
He has increased the number of women appointed to the Curia, the central government of the Holy See, with some in senior positions.
But some campaigners see the changes as "cosmetic" reforms which hide a biased perception of women.
Cathy Corbitt, an Australian member of the executive board of umbrella group Catholic Women's Council (CWC), said the inclusion of female voting members in the Synod was a sign of progress.
But she said the wider view of women in the Church was "very frustrating", much of it taking inspiration from the Virgin Mary, the mother of Jesus.
"The pope still seems to have this blind spot towards women... He seems to regard women in terms of a role, and it's usually in terms of a mother," she said.
- Resistance -
The Synod process is slow -- the current meeting in Rome followed a two-year global consultation, and a second general assembly is planned for next year.
Regina Franken-Wendelsorf, a German member of CWC executive board, said women were hoping for concrete action.
"All arguments and requests are on the table. It's now the Vatican and the Church who have to act!" she said.
While the Church debates, "there are collateral victims, frustration, Catholics who leave because they no longer feel welcomed", added French campaigner Chaumet.
But just as Pope Francis faces resistance in his reform agenda, there is significant resistance to the women's push for change.
"Some American bishops are afraid to follow the path of the Anglican Church," which authorised the ordination of women in 1992, notes one Synod participant, speaking on condition of anonymity.
Another senior Church member, who also asked not to be named, noted that pressure for reform was not equal from all regions of the Church.
"We must not forget that the Church is global," he recalled. "There are expectations (among women) in Europe, but in Asia and Africa, much less."
