The woman was struck at the junction of Stourbridge Road and Highgate Road at around 5.50pm on Wednesday.
West Midlands Ambulance Service said they had received multiple 999 calls from the scene and had sent two ambulances, a MERIT trauma doctor and critical care paramedic, and a critical care car from the Midlands Air Ambulance base in Cosford.
A spokesman for the service said: "When ambulance staff arrived they found a pedestrian, a woman, who had reportedly been involved in a collision with a car. Upon assessment, she was found to have sustained serious injuries.
"The team administered trauma care on scene to stabilise her condition before conveying her on blue lights to Queen Elizabeth Hospital Birmingham for further trauma care."