A 23 year old man was found with multiple stab-wounds on Sunday night on Imperial Way in Croydon.
Police are appealing for information after finding the man with life threatening injuries at around midnight.
He was taken to a South London hospital by air ambulance where his condition remains critical.
Detective chief inspector Lewis Collins said: “A young man had been left in a critical condition after being stabbed repeatedly.
“We believe there were a number of people present who had been to a nearby social event, which then spilled out onto the street.
“We would like to hear from anyone who attended this event and saw what may have led up to the stabbing.
“We also want to hear from anyone who witnessed the attack or saw anyone running from the scene.
“Anyone with information should not hesitate, pick up the phone and call police, or you can call Crimestoppers where you do not have to give your name.
“A young has been left with life threatening injuries and I am appealing to our community to help police find those who were responsible.”
Any witnesses or anyone with any information is asked to call police on 101 or contact via Twitter @MetCC. Quote CAD 9380/28JUL
To give information anonymously contact Crimestoppers on 0800 555 111 or online at crimestoppers-uk.org.