The 31-year-old nun, who is from El Salvador but was a member of a convent in Rieti, north of Rome, gave birth Wednesday shortly after she went into labor, Italy's ANSA news agency reported.
She was taken to the hospital after other nuns at the convent became worried about severe stomach pains she was feeling. At the hospital, the nun denied knowing she was pregnant.
Doctors said both the mother and baby were in good health after the delivery.
Local church leaders said the nun, whose name was not released, will have to leave her convent, the Daily Telegraph reported.
"It would be preferable that she now lead a secular life with her baby, away from religious institutions," said a spokesman for Delio Lucarelli, bishop of Rieti.
Rieti Mayor Simone Petrangeli said the town would offer the woman assistance if she needs it.
"If she needs assistance we will provide it, as we would for anybody," Petrangeli said.