The girl has suffered head injuries after she was knocked down in Pedders Lane, near Ashton Park, at around 10.40am.
She was treated in the road by paramedics before being taken by ambulance to Royal Preston Hospital for urgent treatment.
Lancashire Police said the driver stopped at the scene and no one has been arrested.
A police spokesman said: "We were called to Pedders Lane, Ashton, Preston, following reports a teenage girl had been struck by a vehicle.
"She has been taken to Royal Preston Hospital with head injuries.
"A road closure remains in place at this time."
North West Ambulance Service added: "We responded to a road traffic collision involving a pedestrian following a 999 call at 10.43am.
"A teenage girl was taken to hospital with a head injury."
Pedders Lane was closed both ways between Egerton Road (Ashton Park) and Whinfield Lane until late in the afternoon.
Anyone with information can call police on 101, quoting log 0457 of October 20, 2021.
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