Carrickfergus is a large town in County Antrim, Northern Ireland. It sits on the north shore of Belfast Lough, 11 miles (18 km) from Belfast. The town had a population of 28,141 at the 2021 Census. It is County Antrim's oldest town and one of the oldest towns in Ireland as a whole. Carrickfergus Castle, built in the late 12th century at the behest of Anglo-Norman knight John de Courcy, was the capital of the Earldom of Ulster. After the earldom's collapse, it remained the only English outpost in Ulster for the next four centuries. Carrickfergus was the administrative centre for Carrickfergus Borough Council, before this was amalgamated into the Mid and East Antrim District Council in 2015, and forms part of the Belfast Metropolitan Area. It is also a townland of 65 acres, a civil parish and a barony.

County Antrim is one of the six counties of Northern Ireland, located within the historic province of Ulster. Adjoined to the north-east shore of Lough Neagh, the county covers an area of 3,086 square kilometres (1,192 sq mi) and has a population of 651,321, as of the 2021 census. County Antrim has a population density of 211 people per square kilometre or 546 people per square mile. It is also one of the thirty-two traditional counties of Ireland.