Police were called to Norwood Road near the junction with Station Rise SE27 at 10.30pm on Sunday, 31 December.
Police and London’s Air Ambulance attended and found a 17-year-old male suffering from a single stab wound. He was pronounced dead at the scene at 11.38pm.
Although officers believe they know the identity of the victim, they await formal identification.
Next of kin have been informed and a post-mortem examination will be scheduled in due course.
Detectives from the Homicide and Major Crime Command are investigating. There have been no arrests at this time.
At this early stage, police retain an open mind as to any motive. Enquiries have indicated that an initial altercation may have begun on board a route 68 bus travelling towards Herne Hill shortly before the stabbing.
Anyone who witnessed this incident or has information should call the incident room on 020 8721 4005 or via 101.
To remain anonymous, call the independent charity Crimestoppers on 0800 555 111.