Police were called at 12.16pm to an address in Camberwell, south London, on Thursday to reports of a stabbing.
London Ambulance Service and London's Air Ambulance were also called to Brisbane Street.
They pronounced the teenager dead at the scene.
A 21-year-old man who was known to her has been arrested on suspicion of murder, and is currently in custody at a south London police station.
Her next of kin have been made aware of her death.
A crime scene is in place at the address and the Met's Homicide and Crime Command has been informed.
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