Officers were called to an address in Tinsley Avenue, Old Hill, at 1.45pm on Monday to reports that a man had been seriously assaulted.
The man, aged 43, was taken to Birmingham's Queen Elizabeth Hospital where he remains in a critical condition today, said West Midlands Ambulance Service.
A woman, aged 57, was arrested on suspicion of attempted murder and remained in custody today.
The investigation is at an early stage, but detectives are treating it as a domestic-related incident.
West Midlands Police said enquiries continued today.
An ambulance, paramedic officer, critical care car and an air ambulance all attended the scene, added West Midlands Ambulance Service.