A man, aged 27, was arrested near the scene on suspicion of murder.
A post-mortem will be held at 2pm today at Fulham mortuary.
More top news
The victim was hit as she crossed the road at a pedestrian crossing in Tulse Hill.
The 24-year-old was unarmed and the incident is not being treated as terror-related.
Some platforms have been taken out of service with disruption expected to continue until the end of the day.