Greater Manchester is a metropolitan county in North West England, with a population of 2.7 million. It encompasses one of the largest metropolitan areas in the United Kingdom and comprises ten metropolitan boroughs: Bolton, Bury, Oldham, Rochdale, Stockport, Tameside, Trafford, Wigan, and the cities of Manchester and Salford. Greater Manchester was created on 1 April 1974 as a result of the Local Government Act 1972; and designated a Statutory City Region on 1 April 2011.

Greater Manchester spans 493 square miles (1,277 km²), which roughly covers the territory of the Greater Manchester Built-up Area, the second most populous conurbation in the UK. It is landlocked and borders Cheshire (to the south-west and south), Derbyshire (to the south-east), West Yorkshire (to the north-east), Lancashire (to the north) and Merseyside (to the west). There is a mix of high-density urban areas, suburbs, semi-rural and rural locations in Greater Manchester, but land use is mostly urban — the product of concentric urbanisation and industrialisation which occurred mostly during the 19th century when the region flourished as the global centre of the cotton industry. It has a focused central business district, formed by Manchester city centre and the adjoining parts of Salford and Trafford, but Greater Manchester is also a polycentric county with ten metropolitan districts, each of which has at least one major town centre and outlying suburbs.

For the 12 years following 1974 the county had a two-tier system of local government; district councils shared power with the Greater Manchester County Council. The county council was abolished in 1986, and so its districts (the metropolitan boroughs) effectively became unitary authority areas. However, the metropolitan county has continued to exist in law and as a geographic frame of reference, and as a ceremonial county, has a Lord Lieutenant and a High Sheriff. Several county-wide services were co-ordinated through the Association of Greater Manchester Authorities up until April 2011, when the Greater Manchester Combined Authority was established as the strategic county-wide authority for Greater Manchester, taking on functions and responsibilities for economic development, regeneration and transport.

Before the creation of the metropolitan county, the name SELNEC was used for the area, taken from the initials of "South East Lancashire North East Cheshire". Greater Manchester is an amalgamation of 70 former local government districts from the former administrative counties of Lancashire, Cheshire, the West Riding of Yorkshire and eight independent county boroughs.