The Italian capital joins Naples, Milan and dozens of other towns and cities which already provide for civil unions which ensure formal recognition of the couples in their dealings with the municipal authorities and, in the case of certain companies, with their employers.
"It is a very important day," said Angelo Albanesi, 62, after entering into a union with Pier Giorgio de Simone, the man he has called his husband for the last 35 years.
The two men, both dressed in identical three-piece suits offset by canary yellow flowers, ties and top hats, listened to a short speech by a clearly moved council official, before confirming their identity and signing the
register to loud applause.
"Now we want a law," Albanesi said. Today's celebration is an invitation to the government to act."
Seven male, four female and six mixed couples signed the register at the city hall with some opting to exchange rings in a hall packed with activists and friends and family of the couples.
A bill that would allow for civil unions nationwide is currently being studied by a committee of the Italian Senate but faces considerable opposition from centre-right allies of Prime Minister Matteo Renzi.
Against a backdrop of hostility from the Catholic Church, the government has no plans to follow the lead of Britain and France by legislating to allow gay marriage.