Claudio Cavallo made the announcement during his Sunday service in Borgo San Dalmazzo, a town close to the French border.
The mass would be his last, the 50-year-old priest said, owing to his desire to have a relationship.
“I’ve taken this decision after speaking at length with my superiors. I would like to continue to put my energy into the church, if possible,” Cavallo was quoted in Rai News as saying.
There are reports that Cavallo may be expecting a child with his new partner, the news site said.
The announcement was greeted with applause by parishioners, while Bishop Giuseppe Cavallotto said it had been a “painful decision”.
“We are grateful for the generous service given by Father Claudio in our church. I am certain that the surprise created by his choice will be transformed into understanding and prayers,” Cavallotto was quoted as saying.