A passer-by found the man - aged 35 - at Carnalogue, Louth village, at around 4.40am.
Paramedics were called to the scene where the man was pronounced dead.
His body was taken to Our Lady of Lourdes Hospital in Drogheda for a post mortem examination.
Investigating gardai in Ardee have appealed for anyone who was travelling on the road at Carnalogue between 4.15am and 4.45am to contact them.
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