Giovanny Rendon Bedoya was found injured in Hillingdon Street just before 9.20pm on April 14.
However, he was pronounced dead shortly after.
Six people were arrested on suspicion of murder and three have been bailed pending further enquiries.
The other three have been released with no further action.
Detective Chief Inspector Kate Blackburn said: “On Monday, we received multiple 999 calls, to Hillingdon Street, SE17 reporting that a young man had been stabbed and a number of people were seen carrying knives.
“On arrival, officers found a 21-year-old man who had sustained serious stab injuries
“He was treated by the London Ambulance Service before he was sadly pronounced dead on scene.
“I can now name the victim as Giovanny Rendon Bedoya from Walworth.
“His next of kin has been informed and they are currently being supported by specialist officers.
“Our thoughts remain with them at this incredibly difficult time.
“Following the incident, we immediately made six arrests. Out of the six people arrested, three have been no further actioned and three have been bailed pending further enquiries.
“I would now like to appeal to the public for information.
“Please, if you saw, heard or have any footage following this incident then please come forward. Your information can significantly help our detectives with their investigation.
“We believe there were many people in the area who saw the group, who haven’t yet come forward to speak to police.
“Were you in the Hillingdon Street area on Monday evening? Did you see anyone acting suspiciously? Did you see anyone carrying a knife? If so please contact police.”
Detective Superintendent Emma Bond who is Acting BCU Commander for Lambeth and Southwark policing added: “I recognise that this incident has caused deep concern across our communities.
“I want to reassure you all today that we are working around the clock to find the perpetrators of this attack and to bring them to justice.
“You can expect to see an increased police presence in the coming days and we have more neighbourhood officers on patrol in the surrounding areas this week.
If anyone has any concerns then please do approach these officers, or their local neighbourhood teams, as we are here to help.
“I want to reiterate what DCI Blackburn has said, and urge anyone who has any information about this incident to contact us on via 101 stating CAD7392/14APR.
“Alternatively, to remain 100% anonymous you can call Crimestoppers on 0800 555 111.
“Thank you all for your support and our thoughts and prayers go out the family and friends of the victim involved.”
The investigation remains on-going.
