The incidents happened in Louth, Kerry and Roscommon.
At 9:50pm last night, a teenager was seriously injured in the collision near Listowel and later passed away.
The driver, a woman in her early 20s, and three passengers, all in their late teens, were uninjured.
At approximately 2:50 am, Gardaí attended the scene of a male driver who was fatally injured in Roscommon.
The car of the man aged in his 20s overturned and a post mortem will take place.
Just before 3 o clock this morning, A male pedestrian, aged in his 40s, was fatally injured when struck by a vehicle at Junction 16 southbound on the M1 motorway.
The male driver, aged in his early 50s, and his three passengers, received treatment at the scene for non-life threatening injuries.
Gardaí are urging anyone with information or camera footage to contact them
