"What joy," said Roberto Speranza, leader of Renzi's centre-Left Democratic Party, of the result. "Now it is Italy's turn."
"The moment has arrived, finally, to approve this before the summer's end," said the Democratic senator Andrea Marcucci.
"Ireland is giving us a lesson in civility," said the gay Italian politician Nichi Vendola, president of the Apulia region since 2005.
Laura Boldrini, speaker of the Italian Chamber of Deputies, said Ireland was giving Italy a much-needed push forward. "It is time that Italy has a civil unions law," Boldrini said on Twitter. "To be European means to recognise rights."
Ireland is the 13th EU country to recognise gay marriage. Many countries, such as Germany, allow civil partnerships but are yet to permit marriage, while Cyprus, Greece and most of Eastern Europe still do not officially recognise any form of same-sex union.
Italy's proposed civil partnership law - based on the German model - gives same-sex couples many of the same rights as married couples, as well as the option of stepchild adoption, which allows a partner to adopt the biological child of the other partner.
But the law is stuck in a Senate committee, where it has been bombarded with 4320 amendments, and does not mention marriage.
How the Vatican will respond is unclear. Pope Francis remained silent on the Irish vote during his Pentecost address.