The injured man was taken to Tallaght Hospital where he was pronounced dead.
It is not known how many vehicles were involved or if there are reported injuries.
Gardaí have appealed for wintesses to wish contact Clondalkin Garda station on 01-6667600 or the Garda Confidential Line on 1800-666111.
A man in his 20s has died after a single vehicle road traffic collision in Dublin in the early hours of this morning.
Prasar Bharati chief Vempati given additional charge of Rajya Sabha TV
His resignation has been accepted and the additional charge allocated to Vempati, sources added. Last few weeks have witnessed many changes in the Rajya sabha TV particularly at senior level.
Road closures and diversions are in place.
Gardai are investigating the collision which happened at around 6.20am on Saturday morning, August 12 near Junction 2 Kingswood on the N7 outbound from Dublin to Naas.
It is understood the accident happened at around 6.30am this morning.