County Down

County Down (Irish: Contae an Dúin) is one of the six counties of Northern Ireland, one of the nine counties of Ulster and one of the traditional thirty-two counties of Ireland. It covers an area of 961 mi² (2,490 km²) and has a population of 552,261. It borders County Antrim to the north, the Irish Sea to the east, County Armagh to the west, and County Louth across Carlingford Lough to the southwest.

In the east of the county is Strangford Lough and the Ards Peninsula. The largest settlement is Bangor, a city on the northeast coast. Three other large towns and cities are on its border: Newry lies on the western border with County Armagh. Lisburn and Belfast lie on the northern border with County Antrim. Down contains the southernmost point of Northern Ireland (Cranfield Point) and the easternmost point of Ireland (Burr Point).

It was one of two counties of Northern Ireland to have a Protestant majority in the 2001 census. The other Protestant-majority County was County Antrim to the north. In the 2021 Census, it was the only county with a Protestant background majority, as Antrim has a Protestant background plurality. In the 2021 census, Ards and North Down had the highest number of "No Religion" responses (30.6%) for Northern Ireland.

In March 2018, The Sunday Times published its list of Best Places to Live in Britain, including five in Northern Ireland. The list included three in County Down: Holywood, Newcastle, and Strangford.

The county has two cities: Newry and Bangor. Bangor is the more recent, gaining city status in December 2022.