The 50-year-old woman, who is said to have been suffering from a serious depression, was arrested after she attacked her son at their home in Citta di Castello, near the city of Perugia.
The child was in a critical condition in hospital after undergoing several hours of surgery, doctors said.
He was stabbed eleven times with a kitchen knife in the back and abdomen before the woman's husband managed to wrest the knife from her and call emergency services.
The woman was initially arrested on suspicion of attempted murder. She was transferred to a psychiatric hospital later.