He is being treated in hospital for head injuries sustained outside a bar in the Antrim Road area.
It happened in the early hours of Monday morning.
Police have appealed for anyone who was in the area at the time to contact them.
Meanwhile a 31-year-old man has been injured during an attack in Belfast city centre.
The victim was assaulted outside a pub in the Donegall Street area shortly after 12.15am on Monday.
He was treated in hospital for facial injuries which are not believed to be life-threatening.
The attacker is thought to be in his 20s, between 5'6" and 5'7", of slim build and with short dark hair.
He was accompanied by two other males, both estimated to be 6' tall.