The car and lorry crashed on the M50 between junction 12 and junction 13 southbound on Tuesday afternoon.
Gardai were called to the scene of the collision on the hard shoulder at around 2.50pm.
The driver of the car, a 70-year-old man, collided with the rear of the lorry and was killed.
His body was removed from the scene to Dublin City Mortuary where a post mortem will take place.
The lorry driver was uninjured.
The scene is currently being examined by garda forensic collision investigators and one lane of the motorway is closed.
Gardai are appealing for any witnesses of the collision to come forward.
Gardai are also appealing to any road users with camera footage, including dash-cam, from along this route between 2.30pm and 3.00pm to make it available to them.
Anyone with information is asked to contact Rathfarnham garda station on 01 666 6500.
