Staffordshire Police said the pair were walking along Endon Road on Saturday evening when the incident occurred at about 7.15pm.
Police said passers-by attempted to treat the girl, but she was pronounced dead at the scene.
Her father is being treated for injuries, while the driver of the car is being treated for a head injury.
Inspector Lee Robinson, of Staffordshire Police, said: “The girl’s family will be supported by specially-trained officers and our thoughts are with them at this time.
“We do not yet understand fully what has happened and so I’d urge people to avoid the area while we investigate and please not to speculate as to the circumstances.
“However, I would appeal for anyone who witnessed the incident, or may have CCTV or dashcam footage to get in touch and assist our enquiries.”
Anyone with information is urged to contact police on 101 referring to incident 716 of June 19.
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