A 16-year-old boy was found with stab wounds in Tulse Hill, south London, after police were called to reports of a shooting.
Paramedics tried to save his life at the scene but were unsuccessful.
No arrests have been made and the boy’s next of kin have been informed.
It is the latest in a spate of lethal knife attacks to hit the capital in recent days.
On Wednesday Rocky Djelal, 38, was killed in broad daylight in Southwark Park in Rotherhithe, southeast London.
The following day, 15-year-old Jay Hughes was killed in Bellingham, also in southeast London, by a stab wound to the heart.
Malcolm Mide-Madariola, 17, was fatally stabbed on Friday outside Clapham South Tube station, south London and on Sunday, a man believed to be aged 22 was fatally stabbed in Anerley, also in south London.
The Metropolitan Police has announced it will deploy hundreds more officers across the capital in response to the recent murders.
Metropolitan Police commander Stuart Cundy said: “Only together can we bring down the level of violence in London.”
London mayor Sadiq Khan said it could take 10 years to turn around the problem in the capital, where 117 homicides have been recorded this year.
He also warned children as young as primary school age are now carrying knives and joining criminal gangs.
Agencies contributed to this report