The incident took place in Bassett’s Park at about 12.30am on Saturday, May 26.
The victim, a 19-year-old man, was attacked by a group of about five or six men as he walked across the park.
He suffered injuries to his arm and was taken to hospital for treatment.
It is believed there were a number of people gathered in the park around the time of the incident and officers are appealing for anyone who may have witnessed the it, or noticed any suspicious activity, to contact police.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101, or Crimestoppers anonymously on 0800 555111.