The incident happened outside St James's Park in Barrack Road in Newcastle city centre at around 10.23pm on Tuesday, when the area would have been busy with fans leaving the ground.
The 18-year-old pedestrian became trapped under a double-decker bus and Northumbria Police said she was conscious but suffered rib and spine injuries.
She was taken to hospital where she is in a serious but stable condition.
The force said: "Officers are now keen to hear from anybody who witnessed the collision, which occurred shortly after Newcastle's 2-1 victory over Manchester City.
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"A number of people are thought to have been in the area at the time of the incident, and police are especially keen for anybody who has dashcam footage of the collision to come forward."