Gardai in Newcastlewest in County Limerick are investigating the fatal, which occurred at Rathkeale.
The collision occurred at approximately 3.30am at Blossomhill on the Croagh to Rathkeale Road.
A van collided with a male pedestrian in his 20s. Emergency services were called but the man was pronounced dead at the scene. His body remains at the scene, Gardai said.
The male driver of the van and a female passenger, both in their late 20s, were uninjured in the collision.
The road is closed until at least lunchtime in order to facilitate an examination by Garda Forensic Collision Investigators and diversions are in place.
Gardai wish to appeal for witnesses to contact Newcastle West Garda Station on 069 20650, the Garda Confidential Telephone Line 1800 666 111 or any Garda Station.
Martin Brophy (20), Orla Curry (20) and Angela Kelly (35) died after the vehicle they were travelling in collided with a road sign.