Manchester () is a city and metropolitan borough in Greater Manchester, England, with a population of 545,500 in 2017; the Greater Manchester Built-up Area is the United Kingdom's second-most populous, with a population of 2.55 million. It is fringed by the Cheshire Plain to the south, the Pennines to the north and east, and an arc of towns with which it forms a continuous conurbation. The local authority is Manchester City Council.
The recorded history of Manchester began with the civilian settlement associated with the Roman fort of Mamucium or Mancunium, which was established in about AD 79 on a sandstone bluff near the confluence of the rivers Medlock and Irwell. It is historically a part of Lancashire, although areas of Cheshire south of the River Mersey were incorporated in the 20th century. The first to be included, Wythenshawe, was added to the city in 1931. Throughout the Middle Ages Manchester remained a manorial township, but began to expand "at an astonishing rate" around the turn of the 19th century. Manchester's unplanned urbanisation was brought on by a boom in textile manufacture during the Industrial Revolution, and resulted in it becoming the world's first industrialised city.
Manchester achieved city status in 1853. The Manchester Ship Canal opened in 1894, creating the Port of Manchester and directly linking the city to the Irish Sea, 36 miles (58 km) to the west. Its fortune declined after the Second World War, owing to deindustrialisation, but the IRA bombing in 1996 led to extensive investment and regeneration.
In 2014, the Globalisation and World Cities Research Network ranked Manchester as a beta world city, the highest-ranked British city apart from London. The 2018 Globalisation and World Cities Research Network had Manchester ranked alongside Edinburgh and Birmingham as Beta cities. Manchester is the third-most visited city in the UK, after London and Edinburgh. It is notable for its architecture, culture, musical exports, media links, scientific and engineering output, social impact, sports clubs and transport connections. Manchester Liverpool Road railway station was the world's first inter-city passenger railway station; scientists first split the atom, developed the stored-program computer and produced graphene in the city. Manchester hosted the 2002 Commonwealth Games.