Gardaí are investigating an "unexplained" incident where a man was discovered with serious head injuries in Finglas.
The man, who is in his late 20s, was taken to Connolly Hospital, Blanchardstown, where his condition is critical.
He was found injured on Mellowes Avenue in Finglas at about 8pm by passers-by who alerted gardaí.
The scene has been preserved pending a forensic examination. Gardaí at Finglas are investigating.