The Donegal victim was last night named as Deirdre Burke, 26, from Donegal Town.
Ms Burke was fatally injured in a collision with another car approximately three kilometres outside Donegal Town on the road to Ballyshannon. The accident occurred at approximately 9.40am.
Ms Burke, who was removed to Letterkenny General Hospital, was the driver and sole occupant of one car. Two females in the second car were injured and taken to the same hospital but their injuries are not believed to be life-threatening.
In Co Wexford, a 40-year-old man lost his life in a crash just after midnight.
The single-vehicle collision happened at 12.05am at Ballyellen, between Arklow and Gorey, on the southbound side of the M11.
The car in which he was a passenger crashed into the central median.
The deceased was a passenger in the car. He was pronounced dead at the scene. Two men in their 30s suffered minor injures.
In Co Galway, a 42-year-old man died after he was struck by a car on the Galway to Spiddal road at Ballinahowen, five kilometres west of Barna, at approximately 1.40am.
The pedestrian was pronounced dead at the scene. The driver was uninjured.
Gardaí have appealed for witnesses to the contact them in Donegal Town 074-9740190, Salthill 091-514720 and Gorey 053-9430690.
Anyone with information can also contact the Garda Confidential Line on 1800-666111 or any garda station.
Elsewhere, a 30-year-old Campile woman was fighting for her life following a single-vehicle collision at Camblin, just outside New Ross town yesterday. New Ross Gardaí are appealing for information from anyone who may have witnessed the accident.