The incident happened between 4.30am and 5am on Sunday, December 16.
Two men approached another man in Dalkeith Place and repeatedly kicked and punched him until he was unconscious.
The man was taken to hospital where he required treatment for severe bruising to his face and body.
The first offender was a white man in his 20s, slim, with short dark hair and wearing blue jeans, white trainers and a black hoody.
The second offender was a white man in his 20s, slim, with dark short hair shaved at the sides and the back and wearing blue jeans, white trainers and a grey hoody.
Witnesses or anyone with information should call Northamptonshire Police on 101 or Crimestoppers anonymously on 0800 555111.