Two fire engines and 14 firefighters and officers were called to a fire at a block of flats in Sunray Avenue, Herne Hill last night.
Half of a flat on the first floor of the block was damaged by fire.
One woman was rescued from the flat by crews wearing breathing apparatus. She was treated at the scene by London Ambulance Service before being taken to hospital where she sadly later died.
The Brigade was called at 1814 and the fire was under control at 1912. Fire crews from Brixton and Peckham fire stations attended the scene.
The cause of the fire is under investigation.