A young woman is fighting for life after a hit-and-run in northern NSW.

The 21-year-old was struck by a car on James Street in Glenreagh, a small town in the Clarence Valley about 30km from Coffs Harbour, about 11.40pm on Saturday.

The driver allegedly fled the scene, leaving her seriously injured.

She was treated at the scene before being rushed to hospital in a critical condition.

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A crime scene has been established as investigations continue.

Police are urging anyone with information, CCTV, dashcam or mobile phone footage to come forward.