The man is being treated at Beaumont Hospital, where his condition is understood to be serious.
A man in his 20s is in hospital with a head injury following an assault in Dublin city centre last night.
Gardaí were alerted to a disturbance involving a group of men outside a premises on Usher's Quay shortly before 9 o'clock.
The man is being treated at Beaumont Hospital, where his condition is understood to be serious.
The scene was preserved overnight and examined by scenes of crime officers.
Gardaí are appealing for witnesses to come forward.