Carryduff (from Irish Ceathrú Aodha Dhuibh, meaning 'Black Hugh's quarter') is a small town and townland in County Down, Northern Ireland, about 10 kilometres (6.2 mi) south of Belfast city centre. It had a population of 7,173 people in the 2021 census. Most of the settlement lies within the townland of Carryduff, although part of it extends into the neighbouring townlands of Killynure and Mealough.

One of the earliest references to the settlement dates from 1622, where its anglicised name is written as Carrow-Hugh-Duffe. The original village formed where six roads and a river crossed, and is the site of the ancient Queen's Fort Rath. The road south from Belfast (the A24) climbs out of a gap in the Castlereagh Hills, and splits at Carryduff, one fork (the A7) continuing to Downpatrick (via Saintfield and Crossgar), the other fork (A24) continuing via Ballynahinch to Newcastle towards Kilkeel. In addition, the road from the Ards Peninsula, Newtownards and Comber (the B178) crosses here en route to Hillsborough in the west. All six roads cross the small Carryduff River here (which flows northwards to eventually join the River Lagan at Minnowburn).

The Knockbracken Reservoir was constructed for the Belfast Water Commissioners and opened in 1901, the same year as the Mourne Conduit which carried water from the Kilkeel and Annalong rivers (and later the Silent Valley Reservoir) to Carryduff where it was transported on to Belfast. The Mourne Conduit was replaced by the Aquarius pipeline and associated infrastructure between 1999 and 2004. This new pipeline was laid to the east and north of Carryduff, crossing the A24 at Brackenvale, and bypassing the Knockbracken Reservoir.

The road connections with and proximity to Belfast meant that the town saw some overspill development, from the city, in the 1960s.^{[citation needed]} This period saw several housing developments, the construction of the "Town and Country Shopping Centre", and Carryduff Primary School, leading into the 1970s with the building of the Killynure housing estate by the Northern Ireland Housing Executive. Development along one side of the northbound A24 took place adjacent to the Immaculate Heart of Mary Roman Catholic Church and St Joseph's Primary School, with the Knockbracken Reservoir on the other side.^{[citation needed]}

The 1980s saw expansion continue with Carryduff becoming a commuter town for Belfast workers. Developments continued into the 1990s and included Carryduff Library, Carryduff Shopping Centre. These developments saw the Carryduff River placed inside a culvert for much of its journey through the town. Very little green belt land now remains between Carryduff and the southern border of Belfast, the 1980s having seen the former Matthew Stop Line breached.

In 2018, the disused Knockbracken reservoir became Ireland's largest aqua park, offering a range of water based activities.

The population of Carryduff on census day (21 March 2021) was 7,173 people. Of these:

*respondents could indicate more than one nationality.