West Midlands Ambulance Service received a 999 call reporting that a 66-year-old woman had collapsed and was in cardiac arrest outside a butchers in the Moor Centre, off High Street, in Brierley Hill at around 10.50am on Thursday.
When crews arrived, they found bystanders performing CPR and using a defibrillator.
Ambulance staff continued resuscitation efforts at the scene before the woman was rushed to hospital for further treatment.
Police also closed the road while emergency services were at the scene.
A spokesman for West Midlands Ambulance Service said: "When crews arrived they found a woman in cardiac arrest with bystanders performing excellent CPR. A community public access defibrillator was also being used to administer a shock to the woman’s heart.
"Ambulance staff continued resuscitation efforts at the scene and managed to restart the woman’s heart. The woman, who was in a critical condition, was quickly conveyed on blue lights to Russells Hall Hospital for further emergency care.
“Thank you to the members of the public for their quick thinking, performing excellent CPR and for assisting our crews at the scene. Their actions will have given this lady the best possible chance of survival.”
A West Midlands Police spokesman added: "We were called to reports of a woman in cardiac arrest on Brierley Hill High Street around 11am on Thursday morning.
"The incident attracted a large crowd and we closed the road for safety purposes, allowing quick access for the ambulance services.
"The 66-year-old woman has been taken to hospital for further assessment."
Two ambulances, a non-emergency PTS ambulance, a paramedic officer and a critical care paramedic attended the scene.