County Antrim (Contae Aontroma or simply Aontroim in Irish) is one of the six counties that form the political unit of Northern Ireland, and one of nine counties that historically and geographically constitute the Province of Ulster. It is the 9th largest of the 32 traditional Counties of Ireland in terms of area, and 2nd in terms of population behind County Dublin. Antrim is situated in the north-east of the island of Ireland. It is bounded north and east by the narrow seas separating Northern Ireland from Scotland, the Atlantic Ocean and Irish Sea, south by Belfast Lough and the River Lagan dividing it from County Down, south-west by Lough Neagh, dividing it from County Armagh and County Tyrone, and west by County Londonderry, the boundary with which is the River Bann. Covering an area of 2,844 km², it has a population of approximately 566,000, most of them in and around the Belfast area.

The Glens of Antrim offer isolated rugged landscapes, the Giant's Causeway is a unique landscape and a UNESCO World Heritage site, Bushmills produces legendary whiskey, and Portrush is a popular nightlife zone. The majority of the capital city of Northern Ireland, Belfast, is also in County Antrim, with the remainder being in County Down.