Local government in Northern Ireland in the context of "Newry, Mourne and Down"

The counties of Ireland (Irish: Contaetha na hÉireann) are historic administrative divisions of the island. They began as Norman structures, and as the powers exercised by the Cambro-Norman barons and the Old English nobility waned over time, new offices of political control were established at a county level. The number of counties varied depending on the time period, however thirty-two is the traditionally accepted and used number.

In 1921, upon the partition of Ireland, six of the traditional counties became part of Northern Ireland. In Northern Ireland, counties ceased to be used for local government in 1973. Districts are instead used. In the Republic of Ireland, some counties have been split, resulting in the creation of new counties: there are currently 26 counties, 3 cities and 2 cities and counties that demarcate areas of local government in the Republic.

Reform of local government in Northern Ireland saw the replacement of the twenty-six districts created in 1973 with a smaller number of "super districts". The review process began in 2002, with proposals for either seven or eleven districts made before it was suspended in 2010. On 12 March 2012, the Northern Ireland Executive published its programme for government, which included a commitment to reduce the number of councils in Northern Ireland to 11. The first elections to these new councils were on 22 May 2014.

The structure of local government in the United Kingdom underwent large changes in the 1990s. The system of two-tier local government introduced in the 1970s by the Local Government Act 1972 and the Local Government (Scotland) Act 1973 was abolished in Scotland and Wales on 1 April 1996 and replaced with single-tier authorities. In England, some areas remained two-tier but many single-tier authorities (designated as Unitary Authorities in England) were created. No changes were made to local government in Northern Ireland.

Local government in the United Kingdom has origins which pre-date the United Kingdom itself, as each of the four countries of the United Kingdom has its own separate system. For an overview, see Administrative geography of the United Kingdom. For details, see:

• Local government in England
• Local government in Northern Ireland
• Local government in Scotland
• Local government in Wales

For the history of local government in each country, see:

Derry City and Strabane is a local government district that was created on 1 April 2015 by merging the City of Derry District and Strabane District. It covers most of the northwest of Northern Ireland. The local authority is Derry City and Strabane District Council.

Causeway Coast and Glens is a local government district covering most of the northern part of Northern Ireland. It was created on 1 April 2015 by merging the Borough of Ballymoney, the Borough of Coleraine, the Borough of Limavady and the District of Moyle. The local authority is Causeway Coast and Glens Borough Council.

Mid Ulster is a local government district in Northern Ireland. The district was created on 1 April 2015 by merging Magherafelt District, Cookstown District, and the Borough of Dungannon and South Tyrone. The local authority is Mid Ulster District Council.

Castlereagh (/ˈkɑːsəlreɪ/ KAH-səl-ray) was a local government district with the status of borough in Northern Ireland. It merged with Lisburn City Council in May 2015 under local government reorganisation in Northern Ireland to become Lisburn and Castlereagh City Council, with a small amount being transferred to Belfast City Council.

It was a mainly urban borough consisting mostly of suburbs of Belfast in the Castlereagh Hills (to the south-east of the city) with a small rural area in the south of the borough. Unusually, it had no natural borough centre. The main centres of population are Carryduff, 6 miles (9.6 km) south of Belfast city centre and Dundonald, 5 miles (8 km) east of it.