Statham High Street has been cordoned off by police.
Several police vehiclezs and ambulances rushed to the scene, with an air ambulance also present.
Lambeth Police tweeted: “Police were called at 6.10pm to reports of a fight near #Streatham station.
“Two males (no further details) were taken to hospital for treatment to stab injuries; one of whom is in a critical condition No arrest yet.
“Witnesses pls call 101 ref 5960/07sep.”
One witness wrote on Twitter: “What’s going on in Streatham. It seems pretty big. There’s an air ambulance. Hope everyone’s ok.”
Another added: “Another young person stabbed in Streatham. What is wrong with our young people.”
This is a breaking story. More to follow…