The nun was taken to the Bartolomeo Eustachio hospital in San Severino Marche, central Italy, after complaining of severe stomach pains.
She was rushed to A&E by her fellow sisters and underwent an ultrasound, which revealed she was pregnant, Il Gazzetino reported on Friday.
The nun, thought to be from Colombia, was immediately taken to the maternity ward, where her waters broke and she gave birth after a few hours of labour.
The newborn baby boy is in good health and will stay in hospital temporarily for medical checks. The mother's convent is yet to issue a statement but the sisters have shown interest in taking charge of the baby, L'Unione Sarda reported.
The case bears remarkable similarities to one a year ago, when a Salvadorean nun gave birth after also suffering from stomach cramps.
Roxana Rodriguez was taken from her convent to hospital Rieti, north-east of Rome, where she gave birth. Her fellow nuns were said to be “very surprised” by the arrival of the baby boy, who was named Francesco (Francis) after the Pope.
Rodriguez has since left the convent and lives with a family in Rome, Italian media reported in November. Before being offered accommodation and work in the Italian capital, the former nun spent six months living in nearby Tivoli. She has not yet revealed the name of the baby's father.