Five fire engines and around 35 firefighters were called to a house fire on Ramillies Close in Brixton.
Part of the first floor and roof of a mid-terraced house were damaged by the fire. Firefighters wearing breathing apparatus rescued a woman from the first floor. She was taken to hospital by London Ambulance Service crews suffering smoke inhalation. Sadly, she later died in hospital.
A man left the property and was also taken to hospital suffering smoke inhalation.
The Brigade's 999 Control Officers took 20 calls to the blaze.
The Brigade was called at 1208 and the fire was under control by 1449. Fire crews from Clapham, Brixton, Wandsworth and West Norwood fire stations were at the scene.
The cause of the fire is under investigation by the Brigade and the Metropolitan Police Service.