Officers were called to Ferndale Road, Stockwell, south London, at around 6pm on Friday to reports of a serious assault.
The man was pronounced dead at the scene. He had been stabbed in the chest.
West Yorkshire: A promising teenage rugby league player has been killed in a car crash. Gareth Swift, 19, a hooker with Featherstone Rovers, was killed when the car he was travelling in with team-mate Charlie Tosh crashed on Saturday night.