The 19-year-old was attacked near Natwest bank and Thompson’s Yard at around 4.45am and the men fled the scene.
He was taken to Pinderfields Hospital with serious head injuries where his condition is described as stable.
The scene has been cordoned off by police while forensic examinations are carried out.
The suspects were described as white. One of them was wearing a white T-shirt and the other three were wearing dark clothing.
Det Sgt David Rogerson, of Wakefield CID, said: “Officers are investigating this incident today and we are appealing for any witnesses to come forwards.
“It is believed the victim may have been involved in a prior altercation with the suspects inside the Kooky nightclub and we would like to speak to anyone who saw this incident or who saw the assault on Westgate.
“Clearly, any assault in which a victim suffers head injuries can have very serious consequences indeed and I would ask anyone who has information to contact Wakefield CID on 101 or Crimestoppers, anonymously, 0800 55 111.”