Watch the CCTV footage here from Crimestoppers UK
The charity Crimestoppers is offering the reward, following the attempted murder which happened in April 2023.The 17-year-old suffered life-changing injuries in the early hours of Monday 24 April 2023 when he was attacked on Odstock Road in Penhill.
The victim was taken by air ambulance to John Radcliffe Hospital where it was found he had suffered extensive wounds.At 12.07am, CCTV shows five suspects travelling along Ramsbury Avenue on three electric bikes. Two of the bikes were carrying two people.
They then approached the victim and a sixth unknown suspect joined them at 12.18am. The emergency services were called shortly after this time to treat the victim.
Beth Simpson from Crimestoppers, said: "This is a truly awful case, which is why our charity has now become involved.
"We believe there are people who want to support the young victim, but going to the police is not an option.
"Were you there on the night or have you heard anything about what happened?
"Coming forward is never easy, but if you contact Crimestoppers, you can still make a difference whilst remaining completely anonymous."
At the time Wiltshire Police said: "We are actively investigating this incident with all the resources at our disposal.
“This attack has left a young man with serious injuries and he is currently undergoing hospital treatment. Our thoughts are with his family and friends."