Gardaí suspect the woman driver in her 70s took a wrong exit at a junction resulting in the horrific crash on the Cork-Dublin motorway at about 2.40pm.
Motorists in the other carriageway of the M8 saw her driving her Toyota Land Cruiser south on the northbound carriageway and had beeped and waved frantically to warn her.
The impact of the collision between junctions 13 and 14, just north of Fermoy, was so severe the car was thrown into the air.
The deceased man, aged 28, from Dublin, was driving a Volkswagen Golf. He died at the scene. His female passenger suffered minor injuries and was taken to Cork University Hospital.
It’s understood the woman driver is from Kildorrery, 13km west of Mitchelstown. Gardaí closed off the southbound lanes of the M8 to facilitate the landing of an Aer Corps helicopter which airlifted her to CUH.
Gardaí closed both carriageways of the motorway to facilitate emergency services. Traffic was forced to use the old N8 route. Diversions were in place last night from the junction at Moorepark to the junction south of Mitchelstown. Gardaí later re-opened the southbound lanes.
Gardaí are appealing for witnesses to contact them at Fermoy station on 021 — 4522000, the Garda Confidential Line 1800 666111 or any station.