Police were called at 3.45am on Saturday, 21 August to reports of a disturbance in Clarence Street, Kingston.
Officers attended and found a man in his early 20s with a stab injury to his chest. He was taken to hospital by London Ambulance Service where he was later pronounced dead. His next of kin are yet to be informed.
An 18-year-old man was arrested at the scene on suspicion of murder. He remains in custody at a south London police station.
Detectives from the Met’s Specialist Crime Command are investigating. A crime scene remains in place and enquiries are ongoing.