Police were called at 4.45pm on Tuesday, 12 October to reports of a stabbing in Craneford Way, Twickenham.
Officers and London Ambulance Service (LAS) attended.
At the scene a male, believed to be in his late teens, had sustained knife wounds.
He was taken by LAS to an outer London hospital where he was pronounced dead at 5.54pm
Enquiries are underway to notify his next of kin.
A crime scene and cordons remain in place and at this early stage there have been no arrests.
Anyone who witnessed this incident or has footage is asked to call police on 101 or Tweet @MetCC quoting 5697/12OCT.
Information can also be provided to Crimestoppers, anonymously, by calling 0800 555 111 or visiting www.crimestoppers-uk.org