The accident happened on the N5 between Ballinagare and Tulsk at approximately 5am on Saturday.
Gardai said the victim, a man in his mid 50s, was travelling alone and was pronounced dead at the scene.
The other driver, who was aged in his 40s, was removed to Castlebar General Hospital with minor injuries.
Investigators have appealed for witnesses.
Diversions are in place while Garda forensic collision investigators examine the scene.
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