Three fire engines and around 15 firefighters were called to a fire at a block of flats in Harmood Street in Chalk Farm.
Part of a ground floor flat was damaged by fire. One woman was treated at the scene by firefighters and London Ambulance Service crews before being taken to hospital where she sadly later died.
The Brigade was called at 1437 and the fire was under control at 1506. Fire crews from Kentish Town, Paddington and Holloway fire stations attended the scene.
The cause of the fire is under investigation.