Six fire engines and around 40 firefighters tackled a fire on Pardoner Street in Southwark.
Half of a flat on the first floor of a five-storey residential building was damaged by fire. One woman was rescued by firefighters from a first floor window via a nine-metre ladder. She was taken to hospital by London Ambulance Service crews suffering from smoke inhalation.
The Brigade's 999 Control Officers received 13 calls about the fire.
The Brigade was called at 2257 and the fire was brought under control by 0054. Crews from Dockhead, Dowgate, Old Kent Road and surrounding fire stations attended the scene.
The cause of the fire is under investigation.