An elderly man suffered serious head injuries and a suspected fractured elbow as he tried to stop a thief from stealing his car, police said.
The man, 73, was checking the tyre pressures of his grey Renault Grand Scenic at a garage in Southampton just after 7pm on Thursday when a man got into the vehicle and sped off in it.
The pensioner sustained serious injuries as he fell from the car as he tried to stop the man from driving away from the Shell Garage in Winchester Road, Shirley.
A Hampshire Police spokeswoman said it was believed the man may have had an accomplice.
The pensioner was taken to Southampton General Hospital for treatment.
Police are appealing for any witnesses to the incident, or anyone who was in the area at the time to come forward.
Officers are also keen to hear from anyone who has seen the car, registration CV05 RGO, since it was stolen.
Detective Inspector Dave Jackson, who is leading the investigation, said: "This is a shocking crime and I would urge anyone who can help us find the offender to come forward."
Anyone with information should call police on 0845 045 45 45 or Crimestoppers, anonymously, on 0800 555 111.