A 23-year-old man who tried to stop a fight on the Gold Coast is in a critical condition in hospital after being punched.

When a fight broke out between two groups of men on Orchid Avenue at Surfers Paradise just after 3am, a 23-year-old Oxenford man stepped in to break it up.

Police said he was then punched from behind, fell to the ground and hit his head on the pavement.

The ABC understands that early indications are the man did not know those involved in the scuffle, and the attacker ran at him from behind and punched him in the head.

The other men involved in the fight then fled the scene.

The victim was taken to Gold Coast University Hospital, where he remains in a critical condition this morning.

Two men aged 27 and 29 are assisting police with their investigation.