The accident happened on the Ballycumber Rd, 2km from Ferbane, at about 4pm yesterday. The woman was the only person in the car at the time and no other vehicles were involved.
She was pronounced dead at the scene and her body was removed to the Midlands Regional Hospital in Tullamore.
A section of the road was closed pending an examination by Garda forensic collision investigators.
Anybody with information is asked to contact Banagher Garda Station on 057 9151310, the Garda Confidential Line on 1800 666 111, or any Garda station.
Meanwhile, gardaí are appealing for witnesses following a fatal single-vehicle crash on Christmas Eve in Co Tipperary.
A man in his 60s was killed when his car left the M8 motorway near Junction 7, Cahir, before hitting a ditch at about 4pm. The man had been driving northbound.
A passenger in his 20s was taken to Clonmel Hospital but his injuries were not life threatening.
Anyone with information is asked to contact Cahir Garda Station 052 7445630 or the Garda Confidential Line.
Separately, gardaí have renewed their appeal for information after a 5-year- old girl died in hospital earlier this week, a week after she was seriously injured in a road incident in Co Galway.
The collision, involving three vehicles, occurred on the M6 at Newford in Athenry on Dec 18.