The 46-year-old was found outside a block of flats on Strand Road in Coleraine around 3.50 am on Saturday.
The man was taken to nearby Causeway Hospital for treatment for head injuries.
However, he was pronounced dead on arrival.
Two people have been arrested and are helping police with their inquiries.
Police have appealed for anyone who was in the Strand Road area in the early hours of Saturday morning to contact them 0845 600 8000.