metropolitan county in northwestern England. It encompasses one of the largest metropolitan areas in the country and comprises 10 metropolitan boroughs: Bolton, Bury, Oldham, Rochdale, Stockport, Tameside, Trafford, Wigan, and the cities of Salford and Manchester. Most of the metropolitan county, including the city centres of Manchester and Salford, is part of the historic county of Lancashire. However, parts of four boroughs—Trafford, Manchester, Stockport, and Tameside—belong to the historic county of Cheshire, and part of the borough of Oldham is in the historic county of Yorkshire. From 1974 to 1986 Greater Manchester was an administrative unit. In 1986 the metropolitan county lost its administrative powers, and its constituent boroughs became autonomous administrative units, or unitary authorities. Greater Manchester is now a geographic and ceremonial county without administrative authority.

The Pennines, dissected by deep valleys, rise to the east. Coalfields (mainly sandstones and shales) flanking the uplands form lower plateaus and benches. In the west are glacial clay-covered lowlands traversed by the River Mersey, which rises in the Pennines.

Manchester (Mamucium) was a focal point in the Roman road network. From the mid-17th century, when cotton began to be used in fabric manufacture, Manchester became important in the fustian trade. By the late 18th century, following mechanization and the development of the factory system, the region was dominant in the cotton textile industry. Towns such as Bolton, Bury, Rochdale, and Oldham, specializing in cotton spinning, rapidly expanded, and Manchester became the major market centre. Increased demand for coal resulted in the extensive exploitation of the coalfield in the 18th and 19th centuries, and mining settlements north and east of Manchester and around Wigan grew rapidly. The opening of the Manchester Ship Canal in 1894 made Manchester a seaport, and the area became an important centre for manufacturing and engineering industries. In the second half of the 20th century the region attracted a variety of light industries, transport, and warehousing. The metropolitan area also become an important financial and administrative centre. Peripheral areas include much attractive countryside, and flourishing commuter settlements have developed since World War II. Area 493 square miles (1,276 square km). Pop. (2005 est.) 2,547,600.