A female passenger has died and a second woman has been airlifted to hospital after their car crashed into a river in the Upper Hunter.

Police say a Toyota Landcruiser rolled down an embankment and crashed into the Allyn River about 50 kilometres east of Muswellbrook around 11.00am on Sunday.

The 18-year-old driver managed to free herself from the vehicle – she was winched from the river and flown to the John Hunter Hospital in a stable condition.

Passers-by freed the passenger and commenced CPR before paramedics arrived, however she could not be revived and died at the scene.

The woman is yet to be formally identified.

Investigations into the cause of the crash are continuing and report is being prepared for the Coroner.