The unnamed teenage boy has been rushed to hospital in Brighton after being attacked on the seafront.
Now police are appealing for witnesses after the youngster was attacked in Kings Road, Brighton.
Emergency services rushed to the scene at 2.10am following the incident.
Two men were later arrested by police officers nearby; one by Pavilion Gardens, the other near Jubilee Street.
An 18-year-old man from Brighton was arrested on suspicion of wounding with intent and currently remains in police custody.