At around 1.05am on Saturday 1 August 2020, police were called to reports of a fight on St Petersgate.
Officers attended but the group dispersed prior to their arrival.
A man in his 30s was taken to hospital. His injuries are described as serious.
An investigation is underway.
No arrests have been made.
DC Scott Woods, of GMP’s Stockport district, said: “This fight resulted in a man sustaining serious injuries – he remains in hospital. Our thoughts are with him and his loved ones as he receives treatment.
“We know this incident happened in the middle of a fairly busy town centre at the end of the night out so it’s likely there are a number of witnesses who can assist us with our enquiries.
“I appeal to anyone who was in the area at the time and might have seen/ heard something or has any other information about the fight or who was involved to get in touch with us as soon as possible.”
Anyone with information should contact police on 0161 856 9650 quoting 313 of 01/08/20 or the independent charity – Crimestoppers, anonymously, on 0800 555 111.