Gardaí in the county are appealing for witnesses to a fatal road traffic collision on the N5 Castlebar to Turlough road, which occurred on December 29.
The collision occurred at approximately 4:00pm, involving a car and a van.
The driver of one of the vehicles, a man aged in his 90s, was taken to Mayo University Hospital for treatment of serious injuries, and has since passed away.
The driver of the second vehicle involved, a man aged in his 30s, was taken to MUH to be treated for non-life threatening injuries.
Following examination by Forensic Collision Investigators, Gardaí are appealing to the public for assistance in obtaining information.
Anyone with any information is asked to contact Castlebar Garda Station on 094 903 8200, the Garda Confidential Line on 1800 666 111, or any Garda Station.