The man, who was married and lived in Carriagline, Co Cork, was found in the toilet on Grand Parade, in the city centre, at around 1am yesterday.
He was taken to the Mercy University Hospital, where he was pronounced dead.
It is understood he had been on a night out with family members who raised the alarm when he failed to emerge from the toilet.
Early indications are that the death was not being treated as suspicious, but gardaí were awaiting the preliminary results of an autopsy that was scheduled to take place yesterday afternoon.
The man had no obvious signs of injury or any obvious cause of death but gardaí cordoned off the toilet area to facilitate a technical examination of the scene.
Separately, gardaí in Dublin are appealing for witnesses to an alleged assault in the early hours of yesterday morning after a 24-year-old man was found unconscious on the road at Clonliffe Ave, Dublin 3.
The man, found at aproximately 4.15am, had suffered a number of injuries, including a head injury.
Investigating gardaí believe his injuries may be consistent with an assault. He was transferred to Beaumont Hospital where he is currently being treated for his injuries. It is understood that the injured man may have got a taxi from the Phibsboro area at approximately 2.45am.
The scene at Clonliffe Ave was technically examined by gardaí.
Anyone with information is asked to contact gardaí at Mountjoy Garda Station on 01 666 8600, the Garda Confidential Line 1800 666 111 or any garda station.
They are particularly appealing to anyone who was in the Clonliffe Ave area between to 2.45am and 4.15am to come forward.