The incident happened in Grove Street near Evelyn Street at around 12.35pm today (December 31).
Officers and London Ambulance Service crews attended and found a man who had been stabbed.
He was pronouncded dead at the scene.
No arrests have been made at this early stage and enquiries remain ongoing.
A crime scene remains in place.
A spokesperson for the Metropolitan Police said: “At around 12:35hrs on Wednesday, 31 December officers were called to reports of a stabbing in Grove Street, Lewisham.
“Officers attended the scene alongside the London Ambulance service and London’s Air Ambulance service and treated a 23-year-old man for stab wounds.
“Despite the best efforts of paramedics he was sadly pronounced dead at the scene.
“No arrests have been made at this early stage and enquiries remain ongoing.
“A crime scene remains in place.”
