Oldham is a town in Greater Manchester, England, it lies amongst the Pennines on elevated ground between the rivers Irk and Medlock, 5 miles (8.0 km) southeast of Rochdale and 7 miles (11.3 km) northeast of Manchester. It is the administrative centre of the Metropolitan Borough of Oldham, which had a population of 237,110 in 2019.

Within the boundaries of the historic county of Lancashire, and with little early history to speak of, Oldham rose to prominence in the 19th century as an international centre of textile manufacture. It was a boomtown of the Industrial Revolution, and among the first ever industrialised towns, rapidly becoming "one of the most important centres of cotton and textile industries in England." At its zenith, it was the most productive cotton spinning mill town in the world, producing more cotton than France and Germany combined. Oldham's textile industry fell into decline in the mid-20th century; the town's last mill closed in 1998.

The demise of textile processing in Oldham depressed and heavily affected the local economy. The town centre is the focus of a project that aims to transform Oldham into a centre for further education and the performing arts. It is, however, still distinguished architecturally by the surviving cotton mills and other buildings associated with that industry.

In the 2011 United Kingdom census Oldham Built-up area subdivision, as defined by the Office for National Statistics, had a population of 96,555 and an area of 1,687 hectares (6.51 sq mi), giving a population density of 57.2 inhabitants per hectare (14,800/sq mi), while the Borough of Oldham had a population of 224,897, an area of area of 14,236 hectares (54.97 sq mi), and a population density of 15.8 inhabitants per hectare (4,100/sq mi).