St Paul's Road in Smethwick was closed off for around an hour after the incident, which happened around 9.52am and saw bus services diverted as emergency crews worked at the scene.
The woman was treated by ambulance crews from West Midlands Ambulance Service and subsequently rushed to Queen Elizabeth Hospital in Birmingham for further treatment.
A spokesman for West Midlands Ambulance Service said: "We were called to reports of a collision between a car and pedestrian on St Paul's Road at 9.52am, one ambulance and a paramedic officer attended the scene.
"On arrival we discovered one female patient, the pedestrian, who was treated for potentially serious injuries before being taken to Queen Elizabeth Hospital, Birmingham."
West Midlands Police has been contacted for a comment.