The collision occurred at around 3.30am this morning.
A man in his 50s was taken to Sligo University Hospital in critical condition, while the driver, a man in his 20s, and a teenage boy are being treated for non‑life‑threatening injuries.
The woman was pronounced dead at the scene and her body was taken to Sligo University Hospital, where a post‑mortem will take place.
The coroner has been notified.
The road, which was closed for forensic examination, has since reopened. Gardaí are appealing for witnesses.
Separately, gardaí have named the young mother struck by a car in Co Tipperary on Sunday as Gabrielle O’Donoghue.
The fatal incident occurred shortly after 7pm when Ms O’Donoghue was struck by a car on the R502 at Ballinlassa, between Templemore and Templetuohy.
She was pronounced dead at the scene. The driver, a man in his 20s, did not require immediate hospital treatment.
Local councillor Willie Kennedy said she was the mother of a young son who has now been left without his mother as a result of the tragedy.
Ms O’Donoghue lived between Templetuohy and Templemore and was known in both towns.
“It’s very sad for her family,” said Mr Kennedy. “It’s the loss of a mother. I always considered losing a mother as terrible – losing any parent or anybody – but losing a mother is terrible to a family.
“We hear of road accidents, but we always hear of them further away – it brings it home to you about how badly road accidents affect people. She has parents, she has a child, she has siblings.
“It’s a reminder to us all to be more careful on the roads.”
Gardaí are urging anyone with information or dash‑cam footage to contact them..
In a third incident, a man in his 30s died in a single‑vehicle crash on Powerstown Road in Tyrrelstown, Dublin, on Saturday evening.
The collision occurred at around 6pm.
The passenger, aged in his 30s, was pronounced dead at the scene. The driver, a man in his 40s, was taken to Connolly Hospital with non‑life‑threatening injuries.
Gardaí are conducting a full investigation.
A total of 31 people have died on Irish roads since January 1 — nine more than during the same period last year.
A woman in her 50s has died and three others were injured following a single‑vehicle crash on the N15 at Castlegal, Co Sligo
News in 90 seconds – March 9th