The 33-year-old victim was struck on Tooting Bec Road at the junction of Dr Johnson Avenue, Streatham, at 03:10 BST on Saturday.
Met Police said the man, whose identity is not being released at this stage, was pronounced dead at the scene.
Police have released CCTV images of a silver car they want to trace in connection with the incident.
They would also like to speak to the driver of a Hackney carriage taxi who was seen by witnesses near the scene at the time of the collision.
Det Sgt Phil Hames of the Serious Collision Investigation Unit at Merton said: "I need to hear from anyone who witnessed the collision or has information - including reports of a car which sustained unexplained frontal damage overnight - that may help identify the driver or the vehicle involved."
The appeal number for people to call police is 020 85435157.
A man has been knocked down and killed by a hit-and-run driver in south London.