Greenisland is a town in County Antrim, Northern Ireland. It lies 7 miles north-east of Belfast and 3 miles south-west of Carrickfergus. The town is on the coast of Belfast Lough and is named after a tiny islet to the west, the Green Island. It is a semi-rural community located at the foot of Carn Hill, upon which stands the Knockagh Monument, a war memorial for those from County Antrim who died in the first and second world wars.