A unitary authority is a type of local authority that has a single tier and is responsible for all local government functions within its area or performs additional functions which elsewhere in the relevant country are usually performed by national government or a higher level of sub-national government.
Typically unitary authorities cover towns or cities which are large enough to function independently of county or other regional administration. Sometimes they consist of national sub-divisions which are distinguished from others in the same country by having no lower level of administration.
In Canada, each province creates its own system of local government, so terminology varies substantially.
In Ontario the term single-tier municipalities is used, for a similar concept. Their character varies, and while most function as cities with no upper level of government, some function as counties or regional municipalities with no lower municipal subdivisions below them. They exist as individual census divisions, as well as separated municipalities.
In Germany, kreisfreie Stadt (literally circle-free city) is the equivalent term for a city with the competences of both the Gemeinde (municipality) and the Kreis (district, literally circle) administrative level. The directly elected chief executive officer of a kreisfreie Stadt is called Oberbürgermeister (literally Superior Burgomaster, in English "Chief Mayor" or "Lord Mayor"). The British counties have no directly corresponding counterpart in Germany. This German system corresponds to statutory cities in Austria and in the Czech Republic.
In New Zealand, a unitary authority is a territorial authority (district or city) that also performs the functions of a regional council (first-level division). There are five unitary authorities; they are (with the year they were constituted): Gisborne District Council (1989), Nelson City Council (1992), Tasman District Council (1992), Marlborough District Council (1992), and Auckland Council (2010).
In Poland, a miasto na prawach powiatu, or shortly powiat grodzki (city with powiat rights, or urban county in short) is a, typically big, city which is also responsible for district (poviat) administrative level, being part of no other powiat (e.g. Kraków, Łódź, Wrocław, Poznań). In total, 65 cities in Poland have this status.
In the United Kingdom, "unitary authorities" are English local authorities set up in accordance with the Local Government Changes for England Regulations 1994 made under powers conferred by the Local Government Act 1992 to form a single tier of local 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 not Unitary Authorities thus excluding e.g. the Isle of Wight Council or any other single-tier authority formed under the Local Government Act 1972 or older legislation.
This is distinct from the two-tier system of local government which still exists in most of England, where local government functions are divided between county councils (the upper tier) and district or borough councils. Until 1996 two-tier systems existed in Scotland and Wales, 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 in Northern 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 as parish (in England and Wales) or community councils; such bodies do not exist or have not existed in all areas.
Northern Ireland is divided into 11 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 advisory Northern Ireland Housing Council). Their functions include waste and recycling services, leisure and community services, building control and local economic and cultural development. They are not planning authorities, but are consulted on some planning applications. The collection of rates is handled by the Land and Property Services agency.
Local authorities in Scotland are unitary in nature but not in name. The Local Government etc. (Scotland) Act 1994 created a single tier of local government throughout Scotland. On 1 April 1996, 32 local government areas, each with a council, replaced the previous two-tier structure, which had regional, islands and district councils. Comhairle nan Eilean Siar (formerly the Western Isles Council) uses the alternative Gaelic designation Comhairle. The phrase "unitary authority" is not used in Scottish legislation (whether from the Scottish Parliament or the UK Parliament), although the term is encountered (used either descriptively or erroneously) in publications and in (usually erroneous) use by United Kingdom government departments.
Local authorities in Wales are unitary in nature but are described by the Local Government (Wales) Act 1994 as "principal councils", and their areas as principal areas. 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 a County 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.
Similar to the civil parishes in England, the lowest tier of local government in Wales are the communities. All of the principal councils are fully divided into communities, but not all such communities have established community councils.
There are several types of single-tier governments in the United States. In the states of Connecticut, Rhode Island, and much of Massachusetts, county government has been abolished, and the municipalities (known as New England towns) are the only governing tier below the state government, though the former counties still exist in the ceremonial sense. In some areas, the reverse is true; for example, Howard County, Maryland and Arlington County, Virginia are examples of counties that, despite being densely developed, have no municipalities and are thus the only tier of general-purpose local government.
In Virginia, all municipalities with city status are, by definition, independent from any county. Three other cities across the United States are also independent of any county government: Baltimore, Maryland, St. Louis, Missouri, and Carson City, Nevada. There are also several consolidated cities where the county government and municipal government are unified. San Francisco and Philadelphia are two examples, wherein the city and county are coterminous and have one singular governing body.