Demographics As of the 2021 census, County Antrim had a population of 651,321, making it the most populous county in Northern Ireland, and the second-largest county by population on the island of Ireland, second only to County Dublin.
Demographics As of the 2021 census, County Antrim had a population of 651321, making it the most populous county in Northern Ireland, and the second-largest county by population on the island of Ireland, secon,d only to County Dublin.