The history of Manchester encompasses its change from a minor township in Lancashire to an industrial metropolis in the United Kingdom and the world. Manchester began expanding "at an astonishing rate" around the turn of the 19th century as part of a process of unplanned urbanisation brought on by a boom in textile manufacture during the Industrial Revolution. The transformation took little more than a century.

Having evolved from a Roman castrum in Celtic Britain, in the Victorian era Manchester was a major locus of the Industrial Revolution, and was the site of one of the world's first passenger railway stations as well as important scientific achievements. Manchester also led the political and economic reform of 19th-century Britain as the vanguard of free trade. The mid-20th century saw a decline in Manchester's industrial importance, prompting a depression in social and economic conditions. Subsequent investment, gentrification and rebranding from the 1990s onwards changed its fortunes and reinvigorated Manchester as a post-industrial city with multiple sporting, broadcasting and educational institutions.

Manchester has been on a provisional list for UNESCO World Heritage City on numerous occasions. However, since the 1996 bombing, local authorities have persisted on a course of economic evolution rather than prioritising the past.^{[attribution needed]} This economic evolution is perhaps best illustrated with the 558-foot (170-metre) Beetham Tower which instantly "torpedoed" any possibility of World Heritage City status according to one author. Despite this, areas perceived as internationally important in the Industrial Revolution, such as Castlefield and Ancoats, have been sympathetically redeveloped.

The name Manchester originates from the Latin name Mamucium or its variant Mancunio. These names are generally thought to represent a Latinisation of an original Brittonic name. The generally accepted etymology of this name is that it comes from Brittonic *mamm- ("breast", in reference to a "breast-like hill"). However, more recent work suggests that it could come from *mamma ("mother", in reference to a local river goddess). Both usages are preserved in Insular Celtic languages, such as mam meaning "breast" in Irish and "mother" in Welsh. The suffix -chester is from Old English ceaster ("Roman fortification", itself a loanword from Latin castra, "fort; fortified town").

The Latin name for Manchester is often given as Mancuniun. This is most likely a neologism coined in Victorian times, similar to the widespread Latin name Cantabrigia for Cambridge (whose actual name in Roman times was Duroliponte).

Prehistoric evidence of human activity in the area of Manchester is limited, although scattered stone tools have been found.

There is evidence of Bronze Age activity around Manchester in the form of burial sites. Although some prehistoric artefacts have been discovered in the city centre, these have come from redeposited layers, meaning they do not necessarily originate from where they were found; wider evidence has been found for activity in other parts of the borough. Before the Roman invasion of Britain, the location lay within the territory dominated by the Brigantes and prior to the Roman conquest of the area in the 70s AD, it was part of the territory of the Brigantes, a Celtic tribe, although it may have been under the control of the Setantii, a sub-tribe of the Brigantes.

For the important prehistoric farm site at Oversley Farm, see Oversleyford § Oversley Farm.