Aunitary authority is a type oflocal authority inNew Zealand and theUnited Kingdom. Unitary authorities are responsible for alllocal government functions within its area or performing additional functions that elsewhere are usually performed by a multiple tiers of local government.

Typically unitary authorities covertowns orcities which are large enough to function independently of acouncil or other authority. An authority can be a unit of acounty orcombined authority.

InNew Zealand, a unitary authority is aterritorial authority (district, city or metropolitan area) that also performs the functions of aregional council (first-level division). There are five unitary authorities, they are (with the year they were constituted):Gisborne District Council (1989),Tasman District Council (1992),Nelson City Council (1992),Marlborough District Council (1992), andAuckland Council (2010).^[1][2]

TheChatham Islands, located east of theSouth Island, have acouncil with its own special legislation, constituted (1995) with powers similar to those of a regional authority.^[3][4]

Each of the fourcountries of the United Kingdom uses a different term to describe their unitary authorities. However, theOffice for National Statistics uses the collective term 'unitary administration' to describe all local government areas which operate as unitary authorities.^[5]

InEngland, "unitary authorities" are those local authorities set up in accordance with the Local Government Changes for England Regulations 1994 made under powers conferred by theLocal Government Act 1992 to form a single tier oflocal government in specified areas and which are responsible for almost all local government functions within such areas. While outwardly appearing to be similar, single-tier authorities formed using older legislation are notunitary authorities thus excluding e.g. theCouncil of the Isles of Scilly or any other single-tier authority formed under the older legislation and not since given the status of a unitary authority.

This is distinct from the two-tier system of local government which still exists in most of England, where local government functions are divided betweencounty councils (the upper tier) anddistrict or borough councils. Until 1996 two-tier systems existed inScotland andWales, but these have now been replaced by systems based on a single tier of local government with some functions shared between groups of adjacent authorities. A single-tier system has existed inNorthern Ireland since 1973.

For many years the description of the number of tiers in UK local government arrangements has routinely ignored any current or previous bodies at the lowest level of authorities elected by the voters within their area such asparish (in England and Wales) or community councils; such bodies do not exist or have not existed in all areas.

Northern Ireland is divided into eleven districts for local government purposes. In Northern Ireland local councils have no responsibility for education, road building or housing (though they do nominate members to the advisoryNorthern Ireland Housing Council). Their functions includewaste and recycling services, leisure and community services, building control and local economic and cultural development. Since their reorganisation in 2015 councils in Northern Ireland have also taken on responsibility for planning functions. The collection ofrates is handled by theLand and Property Services agency.

Local authorities inScotland are unitary in nature but not in name. TheLocal Government etc. (Scotland) Act 1994 created a single tier of local government throughout Scotland. On 1 April 1996, 32 local government areas, each with acouncil, replaced the previoustwo-tier structure, which had regional, islands and district councils.Comhairle nan Eilean Siar (formerly the Western Isles Council) uses the alternativeGaelic designationComhairle. While the phrase "unitary authority" is not used in Scottish legislation (whether from the Scottish Parliament or the UK Parliament), the term can be encountered (used either descriptively or erroneously) in a few official publications^[6] and in (usually erroneous) use by United Kingdom government departments.^[7]

Local authorities inWales are unitary in nature but are described by theLocal Government (Wales) Act 1994 as "principal councils", and their areas asprincipal areas.^[8] Various other legislation (e.g. s.91(1)Environment Act 1995) includes the counties and county boroughs of Wales within their individual interpretations of the phrase "unitary authority" as an interpretive not a definitive description. In s.2 of the Act each council formed for a county is allocated the respective English and Welsh descriptions of "County Council" or "Cyngor Sir", each council formed for aCounty Borough is allocated the respective descriptions of "County Borough Council" or "Cyngor Bwrdeistref Sirol"; in all cases the shorter alternative forms "Council" or"Cyngor" can be used.

• In Canada, each province creates its own system of local government, including several analogous to unitary authorities:
  • InAlberta andNova Scotia there isonly one level of local government in that province.
  • InOntario the termsingle-tier municipalities is used, for a similar concept.
• In Germany,kreisfreie Stadt (lit. 'circle-free city') is the equivalent term for a city with the competences of both theGemeinde (municipality) and theKreis (district, literallycircle) administrative level.
• In France, the city ofParis works like a department council and a municipal council. The department councils of the two departments ofCorsica and of the region merged into acollectivité territoriale.
• InPoland, aCity with powiat rights, or "urban county", is a city which is also responsible for district (poviat) administrative level, being part of no otherpowiat (e.g.Kraków,Łódź,Wrocław,Poznań). In total, 66 cities in Poland have this status.
• In Taiwan, most cities have only one tier of local government. Unlike the threecounty-administered cities (Chiayi,Keelung, andHsinchu), they are independent of their surrounding county.Special municipalities, with the exception of a fewmountain indigenous districts within them, are also unitary.
• In the United States, there are several types of single-tier governments.
  • In the states ofConnecticut,Rhode Island, and much ofMassachusetts, county government has been abolished, and the municipalities (known asNew England towns) are the only governing tier below the state government.
  • In Virginia, all municipalities withcity status are, by definition, independent from any county.
  • TheDistrict of Columbia has had no lower tiers of government since theDistrict of Columbia Organic Act of 1871.