Emergency services were called to a serious collision in Lottbridge Drove, Eastbourne, this afternoon (Thursday).
Police, ambulances and firefighters were sent to the scene at the Tesco supermarket at about 2.45pm.
SECAmb (South East Coast Ambulance Service) said teams were called to reports a woman had been seriously injured.
She was taken by road to Royal Sussex County Hospital in Brighton in a serious condition, they said.
The fire service said crews were called to a road traffic collision involving one vehicle.
Firefighters from Eastbourne attended and assisted paramedics with a casualty. Crews left the scene at 3.15pm, the spokesperson said.
No persons were trapped when crews arrived, said the fire service.
One witness said there were two fire engines, two ambulances, and “loads of police” at the scene.
Photos from the incident show paramedics had set up medical tents in the supermarket car park.
SECAmb has been approached for comment.