Four fire engines and around 25 firefighters were called to a fire at a block of maisonettes on Ravensbury Grove in Mitcham.
Part of the ground floor and the staircase in a split level maisonette were damaged by the fire.
A woman was rescued from the first floor by crews wearing breathing apparatus and was taken to hospital by London Ambulance Service crews. Sadly she later died in hospital.
One further woman left the property before the Brigade arrived.
The Brigade was called at 0011 and the fire was under control by 0214. Crews from Wimbledon, Mitcham and Sutton fire stations attended the scene.
The cause of the fire is under investigation by the Brigade and Metropolitan Police Service.