The incident between a pedestrian and a lorry happened in Upper Richmond Road just after 9am today (April 24).
Officers and London Ambulance Service crews attended and found a man injured.
He was taken to hospital for treatment in a life-threatening condition.
No arrests have been made as police enquiries continue.
A spokesperson for Metropolitan Police said: “At 09:07hrs on Wednesday, 24 April, officers were called to Upper Richmond Road, Putney, to reports of a collision between a lorry and a pedestrian.
“Officers attended alongside colleagues from the London Ambulance Service. The pedestrian, a man in his 40s, was taken to hospital where he remains in a life threatening condition.
“No arrests have been made; enquiries continue.”
https://www.yourlocalguardian.co.uk/news/24276231.upper-richmond-road-putney-road-crash-man-fighting-life/