Newcastle is a small town in County Down, Northern Ireland. It had a population of 7,444 in the 2001 Census. The seaside resort lies on the Irish Sea coast at the base of Slieve Donard, one of the Mourne Mountains, and is known for its sandy beach and the Royal County Down Golf Club. The town lies within the Down District Council area.
The town aims to promote itself as the "activity resort" for Northern Ireland and its most special attribute is its location at the foot of Slieve Donard. The town has benefited from a multi million upgrade which makes it a high quality seaside attraction. The town is twinned with New Ross, County Wexford, in the Republic of Ireland.