A 43-year-old man was arrrested on suspicion of attempted murder after an incident on Sandy Lane, Caldicot, in the early hours of Saturday morning.
Officers attending the scene found a 47-year-old woman who had suffered serious stab wounds and was subsequently taken to Newport's Royal Gwent Hospital.
A spokeswoman for Gwent Police said on Saturday afternoon that she was in a serious but stable condition.
Gwent Police officers were called to the area at around 1am following reports of a disturbance.
The 43-year-old man remains in police custody with officers not looking for anyone else in connection with the incident.